Highway Needs of the National Defense/Status of Improvement of the Interstate Highway System and Its Service to Traffic
STATUS OF IMPROVEMENT OF THE INTERSTATE HIGHWAY SYSTEM AND ITS SERVICE TO TRAFFIC
Extent of the System
The existing roads and streets presently serving as routes of the National System of Interstate Highways, shown in figure 1, have a total length of 37,800 miles. Of this total, 3,778 miles are composed of streets in “urban areas” including all cities of 5,000 or more population by the 1940 census, and 2,191 miles consist of streets in towns of less than 5,000 population. The total included mileage of streets in urban places is, therefore, 5,969 miles. The remainder of the system as presently designated consists of 31,831 miles of rural roads located outside of the limits of all towns and urban areas.
MILEAGE AND TRAFFIC
The 5,969 miles of urban streets included in the system represent about 2 percent of the 316,536-mile total length of all city streets. The 31,831 miles of the system’s rural-road sections represent 1 percent of the country’s total of 3,009,617 miles of rural roads.
In 1948, the 5,969 miles of urban streets included in the system served an estimated 20,740 million vehicle-miles of travel. This traffic, served by 2 percent of the total city-street mileage, was almost 11 percent of the traffic served by all city streets.
The 31,831 miles of rural roads included in the system served during 1948 an estimated 33,965 million vehicle-miles of travel. This traffic, served by 1 percent of the total rural-road mileage, was 17 percent of the traffic served by all rural roads.
The existing streets, constituting the urban sections of the system, carried in 1948 an average traffic of 9,500 vehicles daily. This compares with an average for all other city streets of about 1,600 vehicles per day.
Existing roads constituting the designated rural sections of the system carried in 1948 an average traffic of 2,915 vehicles daily. This compares with an average of about 1,295 for the entire Federal-aid primary highway system, 1,155 for the State highway systems (exclusive of local roads under State control), and 53 vehicles per day for all rural roads not included in any of these systems.
The 1 percent of the country’s total rural-road mileage, which forms the rural portion of the designated interstate system, served in the several States an average of 2714 percent of the travel on all rural roads in each State by vehicles registered in other States. The designated rural system is thus shown to be outstandingly of service to that portion of the country’s highway traffic that can be classed as interstate in character. POPULATION SERVED
Of the total urban population of 83,766,379 in the United States in all incorporated places, as shown by the 1940 census, 54,378,200, or 65 percent, was resident in cities and urban places connected by the designated interstate system. These included all of the cities of 250,000 or more in es 49 of the 55 cities that had population between 100,000 and 250,000, 69 of the 107 cities that had population between 50,000 and 100,000, and 2,538 smaller cities, towns, and urban places.
Routes of the system traversed for some distance 1,160 of the 3,076[1] counties in the United States. In these counties traversed, the 1940 population was 23,953,461, or 50 percent of the total rural population of the country.
BRIDGES
On the entire system, as presently designated, there are 12,048 bridges. Of these structures 10,524 carry interstate routes over streams or natural water courses; 979 are over railroads; 384 span other highways. The remaining 161 are structures spanning two or more of the above kinds of crossings.
- ↑ For statistical purposes, parts of Yellowstone National Park in Idaho and Montana are counted as separate counties. For the same reason the District of Columbia is included as a county, and various independent cities, e. g., 24 in Virginia, are lumped in the respective counties of which they might logically be considered geographically a part.
Of the bridges over streams 1,281 are on urban sections of the system, 9,243 on rural sections. Of the bridges over railroads 396 are on urban sections, 583 on rural sections of the system. Of those over highways 217 are on urban sections; 167 on rural portions. Of the 161 remaining structures, 104 are on urban portions and 57 are on rural sections. Of the total of 12,048 structures carrying the interstate routes, 1,998 are on urban sections and 10,050 on rural sections of the system.
Additional to the 12,048 bridges which carry the interstate routes over streams, railroads, and other highways, there are 943 bridges, 562 on urban and 381 on rural sections of the system, which carry railroads over the interstate routes; and 336 structures, 185 on urban and 151 on rural sections, which carry other highways over the interstate routes.
Status of Improvement of Interstate Highways
The system, as generally described above, consists of those existing roads and streets now commonly used for travel along the general lines of the designated interstate routes. All of these roads and streets were reviewed in detail by the State highway departments. Field surveys were made, as necessary, and these were supplemented by reliable records to prepare an inventory of the physical conditions existing on all parts of the system and an enumeration of the traffic which each section served in 1948. These data were uniformly compiled by all of the State highway departments and reported in detail to the Public Roads Administration, where they were summarized for the system as a whole.
Figure 2 shows a sample of the graphical highway data sheet on which the desired information was reported by the State highway departments. Supplementary to the report in this form, the States coded many of the items in preparation for mechanical tabulation, and this coding was verified, and the data tabulated and analyzed, by the Public Roads Administration.
The following pages summarize the more significant information revealed by the survey.
TYPES OF SURFACES
All but 24 miles of the system as it exists at present have been surfaced. Of the small unsurfaced mileage, 9 miles are urban and 15 miles are rural. Of this unsurfaced mileage, all but one-half mile had been graded and drained at the time of the survey.
Low-type surfaces
A small mileage—6 miles, of which 2 miles are urban and 4 miles rural—is surfaced with selected soil. These are the most primitive surfaces now existing on the system. With 138 miles of untreated gravel or stone surfaces, 3 miles in urban and 135 miles in rural areas, they constitute a total of 144 miles classed as of low-type surface. Of this total, 5 miles are urban and 139 miles rural.
Intermediate-type surfaces
Surfaces classed as of intermediate type, consisting of three low-cost types of bituminous surfaces, exist on 4,990 miles of the system, of which 417 miles are in urban and 4,573 miles are in rural areas. High-type surfaces
By far the greater part of the system—32,642 miles—is paved with surfaces of high type. Of these surfaces 16,091 miles are high-type bituminous pavement, 2,390 miles in urban, and 13,701 miles in rural areas.
A mileage nearly as large—15,230 miles—is paved with portland cement concrete; 2,478 miles in urban, and 12,752 miles in rural areas. The remainder, 1,321 miles, is surfaced principally with brick or block pavements and different high-type surfaces in combination. Of this latter mileage, 670 miles are in urban, and 651 miles are in rural areas.
AGE OF SURFACES
While, as stated above, a very large part of the system is surfaced with pavements classed as of high type, and only an insignificant mileage remains unimproved, these facts of surface-type classification do not reflect the condition of the surfaces of the highways, and there is no convenient gage by which conditions so various as those of the surfaces existing on the system can be measured and intelligibly recorded and classified.
Average age
Perhaps the best indication of the condition of the surfaces may be found in their ages, which for all rural portions of the system are definitely known. The average age of all surfaces on rural sections of the system is 12 years. Many, of course, are much older. The roadways on which these surfaces are laid are nearly half again as old, averaging about 17 years of age. In other words, the average mile of rural highway on the interstate system consists of a surface that was last improved in 1937 and a roadway upon which the last major improvement of alinement and grade was made in 1932. These are most significant facts in view of the increases in traffic and the demands of safe operation that have occurred during these intervals.
Age by type of surface
Of the 27,104 miles of high-type pavement on rural sections of the system, 3,743 miles or 14 percent are more than 20 years old. Between 10 and 20 years of age there are 12,614 miles, or 46 percent of the total; and only 10,747 miles, or 40 percent, are less than 10 years old.
The surfaces of intermediate type average even older. Of the rural surfaced mileage of this class, totaling 4,573 miles, 614 miles, or 13 percent, are more than 20 years old; 2,698 miles, or 59 percent, are between 10 and 20 years of age; and only 1,261 miles, or 28 percent, are less than 10 years old.
The low-type surfaces on the system, being of less durable character, naturally are of lesser present age. Of the surfaces of this class, totaling 139 miles on rural sections of the system, only 3 miles, or 2 percent, are more than 20 years old; 50 miles, or 36 percent, are between 10 and 20 years old; and 86 miles, or 62 percent, are less than 10 years of age.
WIDTHS OF SURFACES AND SHOULDERS
Of the 5,969 route miles of the system in urban places, 695 miles are made up of pairs of one-way streets, the street mileage of which is twice the route mileage. The remainder, 5,274 miles, consists of two-way streets.
Urban surface widths
Of the street mileage of one-way streets, a total of 1,390 miles, only 168 miles are as much as 40 feet wide; 366 miles are between 30 and 40 feet wide; the largest fraction, 835 miles, are between 20 and 30 feet wide; and 21 miles are less than 20 feet in width.
Of the two-way streets, 2,069 miles are less than 30 feet wide, 1,011 miles are between 30 and 40 feet wide; 1,747 miles are between 40 and 60; and 447 miles are more than 60 feet wide.
Rural surface widths
Of the 31,831 miles of the system in rural areas, 31,816 miles are surfaced, and of this mileage 27,669 miles have two-lane surfaces. There are 241 miles on which the two-lane surface is less than 18 feet wide, and an additional 5,868 miles on which it is between 18 and 20 feet wide. More than 40 percent of the existing two-lane surfaces, 11,637 miles, are between 20 and 22 feet wide; 4,694 miles are between 22 and 24 feet; and only 5,229 miles are as much as 24 feet in width.
Width of shoulders
Of the 31,831 miles of the system in rural areas, 421 miles are built without shoulders, curbs replacing this normal feature of rural road design. Of the 31,410 miles built with shoulders, 6,273 miles have shoulders less than 4 feet wide; 15,990 miles have shoulders between 4 and 8 feet in width, and on 9,147 miles the shoulders are 8 feet wide or more.
CURVATURE
Of the total length of the system in rural areas, 1,949 miles are located in areas classed as mountainous; 12,572 miles are located in areas of rolling topography; and 17,310 miles lie in generally flat or level areas.
Frequency and sharpness of curves
Both the number and the sharpness of curves, as would naturally be expected, are greatest on the sections of the system in mountainous areas. On the 1,949 miles in such areas there are 5,988 curves, or more than three for every mile, that are sharper than 3 degrees. On the sections in rolling topography, 12,572 miles in total length, there are 9,435 curves sharper than 3 degrees, a frequency of 1 to every 1⅓ miles; and on the 17,310 miles in flat topography the number of curves exceeding 3 degrees is only 6,473 or not much more than 1 in every 3 miles.
On the entire 31,831-mile extent of the system in rura] areas curvature in excess of 3 degrees occurs at 21,896 points, an average of a little more than 1 in each 1½ miles of the system. All other curvature on the rural system is not greater than 3 degrees.
A 3-degree curve has a radius of about 1,900 feet. It is a curve that can be rounded with safety at 70 miles an hour; but any curvature of greater degree requires for safety a reduction of vehicle speed below 70 miles an hour. On a curve of 11 degrees (radius about 520 feet) it is unsafe to travel above 50 miles an hour. Curves sharper than 11 degrees occur On mountainous sections of the system with a frequency of more than once per mile. About once in each 1⅓ miles in these sections in mountainous areas a curve is encountered which is sharper than 14 degrees, which is safe for a speed of only about 40 miles per hour.
Curvature and safe speed
If by reason of the frequency of occurrence of curves in excess of 11 and 14 degrees, the mountainous sections of the system in their present state were characterized, on the basis of curvature alone, as generally safe for speeds of 40 to 50 miles an hour, the same curve-frequency test applied to the sections in rolling topography would rate them as safe on the average for 60- to 70-mile speed. This, it should be added at once, is a rather broad generalization, because there are curves in some places on the system in rolling topography that are about as sharp as any in the mountainous areas. By similar broad generalization and like qualification, the greater part of the system in flat rural areas can be characterized, on the basis of curvature alone, as good for speeds approaching 70 miles an hour.
Since adequacy of design is determined by a number of conditions besides curvature, the general characterizations indicated in respect to curvature must be strictly so limited. All conditions considered, a very small part of the system as it now exists is satisfactory for travel at 70 miles an hour.
GRADES
The steeper grades on a highway become serious impediments to movements over the highway only when they are of substantial length. Vehicles climb short, steep grades on the momentum gathered on approaching down grades or stretches of level or light upgrade.
Classification of grades
For this reason, in the survey of the grades existing on the system, grades of various steepness were recorded as significant only where they exceeded certain lengths, varying with the rate of gradient. The determining lengths were 2,000 feet for grades between 3 and 4 percent, 1,000 feet for grades between 4 and 5 percent, and 500 feet for grades of over 5-percent steepness.
Grades of the several degrees of steepness were recorded when, either as continuous sections of single gradient or as an average of different grades within a continuous section, they extended to at least the determining lengths corresponding to the three grade classes. It follows that no grades of 3 percent or less were recorded except as, in combination with steeper grades, they averaged above 3, 4, or 5 percent for the required determining distances.
Grades steeper than 3 percent
As thus defined, there are 6,646 grades totaling 2,770 miles on the entire designated system that are steeper than 3 percent; 656 of these grades, totaling 226 miles, are on urban sections of the system; 5,990, totaling 2,544 miles, are on the rural portion of the system.
Steeper than 6 percent, there are on the entire system 668 grades, totaling 243 miles, of which 108, totaling 28 miles, are on urban sections, and 560, totaling 215 miles, are on rural sections.
The steepest grades
The two steepest grades on the entire system are both in urban areas. Both average more than 10 percent. One is on US Route 40 in the town of Old Washington, Ohio (population, 297). The other is on US Route 70 in Marion, N. C. (population, 2,889).
The grade on US Route 40 averages just over 10 percent on a length of about one-third mile, but it includes a section of 14-percent grade one-fifth mile in length. An hourly traffic of 430 vehicles traveled this grade, up and down, in 1948. The road has an 18-foot two-lane bituminous pavement of high type.
The grade on U S Route 70 averages almost 11 percent for a distance
of 0.15 mile. The up-and-down hourly traffic on this grade in 1948
was 555 vehicles. The street has a 55-foot concrete pavement.
The longest grade
The longest grade on the entire system is on U S Route 99, south of Bakersfield, Calif. It is 20 miles long and averages 4 percent over the entire length. Included, however, are two 6-percent grades, totaling more than 6 miles, and two 5-percent grades, totaling one-half mile. On the grade there are 16 curves, 12 between 3 and 4 degrees and 4 between 4 and 5 degrees. Six miles of the grade are surfaced with an undivided pavement 30 feet wide; the remaining 14 miles have a divided four-lane pavement, varying between 20 and 25 feet wide on each side. The average daily traffic in 1948 was 8,650 vehicles, of which 18 percent were trucks and busses.
STOPPING SIGHT DISTANCE
In the 31,831 miles of the interstate system as it is presently improved, there are 21,028 sections of various length, totaling 2,087 miles, on which the road ahead is not visible for a distance sufficient to permit the stopping of vehicles moving at desirable speeds before striking low-lying objects and holes or other dangerous surface conditions. The mileage deficient in this respect is nearly 7 percent of the total rural mileage of the system. Safe operation on these sections can in some cases be provided for by the removal of sight-distance obstructions such as trees, cut slopes, and buildings. In the great majority of cases, however, correction can be made only by changes of the alinement or profile of the road, or both, to provide flatter horizontal and vertical curves.
PASSING SIGHT DISTANCE
Stopping sight distance is necessary for safety of operation on all roads. On two-way roadways of two and three lanes it is equally desirable that the road ahead be visible for a sufficient distance to permit drivers to move into the left or central lane long enough to pass other vehicles without danger of collision with oncoming vehicles. The lack of such safe passing sight distance is the principal reason for the formation of queues behind slow-moving vehicles and a major cause of the obsolescence of highways built in the past. Where passing sight distance is inadequate, safe drivers are restricted in their freedom of movement to almost the same degree as if the lane used for passing were filled with oncoming vehicles; and those who attempt to pass under these conditions are reckless drivers who all too often cause grief to others as well as themselves as a result of their action.
The sight distance required for safe passing varies with the speeds of the passed and passing vehicles and the speed of a possibly oncoming vehicle. For safe passing at the speeds that should be accommodated on the interstate system, a clear sight distance of 1,500 feet ahead is essential. It is not necessary that the road ahead be visible for this distance from every point on the highway. This is a condition that could be fulfilled only at a prohibitive cost. It is essential, however, for reasonable safety, that 1,500 feet of sight distance shall be available continuously over sections of the road sufficiently long to permit the completion of passing maneuvers, and that such sections shall recur at intervals sufficiently short to prevent the building up of queues of vehicles waiting to pass.
One of the more serious deficiencies of the interstate system as it exists today is found in the fact that there are 7,324 miles of the 29,276 miles in rural areas surfaced for two and three lanes—one-fourth of the entire mileage—on which this condition of safe travel is not present. STOP SIGNS AND TRAFFIC LIGHTS
The free flow of traffic on the system at present is interfered with at numerous points, especially in urban areas, by stop signs, stop- and-go lights, and flashing beacons. On rural sections of the system there are 132 stop signs requiring the halting of vehicles moving on the interstate highway. Besides these, on rural sections, there are 394 traffic lights of the stop-and-go variety and 302 cautionary flashing beacons. These stop signs and signals on rural sections of the system are encountered mainly in the more populous areas and in the vicinity of cities. Most of the 31,831 rural miles of the system is entirely free of such traffic control.
Conditions in cities
In cities the condition is very different. On the 5,969 miles in urban places there are 9,036 installations of such signs and signals, an average of 3 for every 2 miles. In the larger cities—those over 5,000 population—they average 2 to the mile. In the largest cities they are, of course, of still more frequent occurrence.
Stopping necessitated by these signals accounts in part for the very slow movement of traffic that is found to exist on urban sections of the system. In larger part, perhaps, the slow speed is occasioned by the many other obstacles to movement encountered. Among these are many unsignalized cross streets, jay-walking pedestrians, the midblock halting of vehicles to load or unload, the maneuvering of vehicles into and out of parking spaces, and the double parking of vehicles.
Speed of movement in cities
All of these causes together result, as shown by actual running tests made in all cities of 5,000 or more population, in an average speed of movement on sections of the system in cities of these sizes of only 18.1 miles per hour during the hours of peak traffic and 23.5 miles per hour during the off-peak hours. There is almost no variation from these averages in cities, from the smallest to the largest. Since about one-third of the day’s traffic is known to pass over the streets during the two peak periods, totaling about 4 hours a day, the average speed of the all-day movement can be readily computed as 21.7 miles per hour, a speed at which it takes 2.77 minutes for a vehicle to travel a mile.
Time savings through improvement
The annual travel on sections of the system in cities of 5,000 population or more is 17,180 million vehicle-miles. The aggregate travel time for this movement at the prevailing speeds is 47,589 million vehicle-minutes. If the average speed of the movement were increased to 35 miles an hour, the minimum that would be required if the streets were adequately improved, this time would be reduced by 20,919 million vehicle-minutes annually, taking into account the increased traffic that would have used these streets had they been so improved, and the shortened mileage resulting from the improvements At a cent a minute, this time saving would be worth more than $209 million annually, a sum about four-fifths as great as the annual cost of urban improvements hereafter proposed, spread over 20 years. In addition, the elimination of much stopping and starting would effect tangible and material savings of a larger order in reduced gasoline consumption and vehicle maintenance costs.
RAILROAD GRADE CROSSINGS
A total of 2,047 grade crossings of railroads remain on the roads and streets that presently form the designated system. This is only 17 less than the number of grade crossings that have been eliminated by the construction of grade-separating bridges.
Of the grade crossings remaining, 785 are crossings of railroad sidings or spur tracks only, but 1,262 are crossings of main-line tracks. Of these main-line crossings, 542 are crossings of single-track lines on which there are six or more train movements daily; 218 are crossings of two or more main tracks.
Capacity and Dimensions of Bridges
LOAD CAPACITY
With few exceptions the strongest of existing highway bridges are of the design designated as H20-S16. Such bridges are designed to support live loads equivalent in stress effect to those imposed by a 20-ton tractor truck of 14-foot wheel base coupled to a semitrailer with 16 tons on its single axle 14 feet to the rear of the rear axle of the tractor. The gross load of the combination, imposed over a length of 28 feet, is 72,000 pounds. Such bridges will carry, without increase of stress, longer vehicles of much greater gross weight and will support without failure the infrequent passage of heavy military vehicles, if the weight is properly distributed.
Bridges of other design strength are similarly designated as H15-S12, signifying an assumed design loading equivalent to that of a tractor-semitrailer combination of 27 tons gross weight, and as H20, H15, H10, etc., signifying the assumption of design loadings equivalent to those of single trucks of 20, 15, and 10 tons gross weight. In each case the wheel base of the combination assumed is 28 feet, and that of the single truck is 14 feet. All such bridges will safely carry vehicles of gross weight considerably in excess of the design vehicle if the weight is distributed over greater length.
Bridges of adequate capacity
Of the 12,048 bridges presently carrying the interstate routes over streams, railroads, and other highways, 1,607 are designed for or rated as of H20-S16 load capacity. Two hundred and nineteen of these are on urban sections of the system; 1,388 are on rural sections. Bridges rated as H20 number 2,207, of which 763 are on urban, and 1,444 on rural sections of the system. A total of 7,526 of the existing bridges, 887 on urban sections and 6,639 on rural sections of the system, are rated in classes from H15 to H19. These existing bridges on the system will all support with complete safety the frequent passage of vehicles conforming in weight to any of the State laws in current effect. None but the H20-S16 bridges is designed to carry some of the more extreme loads known to be moving over the system.
Bridges of inadequate capacity
A total of 677 of the existing bridges, 110 on urban, and 567 on rural sections of the system, are rated as of less than H15 capacity. All of these must be considered as of inadequate capacity; and 130 of them, 30 in urban, and 100 in rural areas, which are rated below H10 must be regarded as dangerously inadequate. Of all the bridges on the system it has been impossible to determine the load-capacity rating of only 31, of which 19 are on urban, and 12 are on rural sections of the system.
WIDTHS OF BRIDGES
From the foregoing it is apparent that, in respect to load capacity alone, most of the existing bridges on the system are reasonably adequate. Unfortunately, an equally favorable report cannot be made in respect to other features of their design and location.
Width deficiencies
At the extreme of inadequacy are 52 two-way bridges which are less than 18 feet in horizontal clearance. Thirty-one of these bridges, each more than 80 feet long, are classed as long bridges. And, most unfortunately, 14, of which 9 are long bridges, are classed among the strongest of the existing bridges by ratings of H20. Two of these bridges less than 18 feet wide somehow managed to carry an hourly traffic in 1948 of more than 800 vehicles.
The widths of the existing bridges cover such a wide range, the relation of bridge width to the width of existing approach pavement is so various, and, moreover, the relation of the bridge width to the volume of traffic served is so complicated, that it is impossible to summarize in brief statement the many evidences of existing width inadequacy.
Here it may be sufficient to say that of the total of 10,050 bridges carrying the interstate routes in rural areas, only 1,863 conform fully to the standards of width regarded as reasonable for highways of such importance. With some tolerance, 1,517 additional structures may be accepted as substantially adequate; but 6,670 of the existing rural bridges, about two-thirds of the total number, are entirely too narrow.
Underpasses
A similar condition of width inadequacy affects the bridges which carry railroads and other highways, forming underpasses for the interstate highways. Of the 381 bridges which carry railroads over rural sections of the interstate system 316 do not provide sufficient horizontal clearance for the highway as it should be designed; and of 151 bridges carrying other highways over, 41 allow insufficient clearance for a proper width of the interstate highway.
VERTICAL CLEARANCE
In regard to vertical clearance, the situation is much better; in fact, extremely good. Most of the bridges carrying the interstate routes are of the deck type, with no overhead restriction whatever. The commonly accepted standard of vertical clearance for bridges, and the standard which is regarded as adequate for the interstate system, is 14 feet.
There are only 71 of the existing bridges carrying rural routes of the system that provide vertical clearance less than 14 feet. Eighteen of the bridges inadequate in this respect are structures of H20 capacity rating; 53 are of lesser capacity rating.
There are, however, on the rural system 2 highway overpasses, and 70 railway overpasses that provide vertical clearance less than 14 feet; and on the entire system, both urban and rural, there are 320 places where 14 feet of vertical clearance is not available. One hundred and seventy-five of these places are in urban areas and 145 in rural areas.
MATERIALS OF CONSTRUCTION
The 7,875 concrete bridges on the system are the most numerous of any single material, and their aggregate length, 191 miles, is slightly greater than that of the steel bridges. Only 149 of the concrete bridges are between 100 and 200 feet in length and only 93 are 200 feet and longer. Only 232 of the concrete bridges are of load capacity less than H15.
Twelve hundred and forty-five of the existing bridges are wooden structures, their aggregate length 29 miles. There are 47 of these bridges that are rated as of H20 capacity or more. Many are much weaker; in fact, the number of wooden bridges rated below H15 capacity, a total of 256, exceeds the number built of any other material.
Of material other than steel, concrete, or wood there are 127 existing bridges, mostly of stone masonry. These have an agegregate length of. only 7 miles. Nine are between 100 and 200 feet and 14 are 200 feet or more in length. Only two are rated at less than H15 capacity.
The aggregate length of all of the 12,048 bridges on the system is 2,194,592 feet, or about 416 miles.
Tunnels on the System
TUNNELS IN RURAL AREAS
Seven tunnels are in Pennsylvania. They range from 3,512 to 6,792 feet in length, and all provide 23 feet horizontal and 14.3 feet vertical clearance. All are approached by four-lane divided highways, and carried an hourly traffic of 800 to 1,000 vehicles in 1948.
The remaining two tunnels in rural areas are the 531-foot Newcastle tunnel in California, and a 394-foot tunnel in Idaho. These have horizontal clearances of 30 and 20 feet, respectively. The vertical clearance of the Newcastle tunnel varies from 11½ to 20.7 feet; the minimum vertical clearance of the tunnel in Idaho is 15 feet. Hourly traffic in 1948 was 864 vehicles on the former and 171 on the latter.
TUNNELS IN URBAN AREAS
The Bankhead tunnel, a toll facility on US Route 90 in Mobile, Ala., is 3,389 feet long and has a minimum vertical clearance of 12 feet. Although carrying an hourly traffic in 1948 of 1,030 vehicles, and approached at one end by a 50-foot pavement, the tunnel is only 21 feet wide.
The 540-foot Yerba Buena tunnel in California lies between the two sections of the San Francisco-Oakland Bay toll bridge. This tunnel, part of US Route 40, carried 7,740 vehicles hourly in 1948. Average daily traffic for the year was 70,897 vehicles. The tunnel has two levels, the upper carrying six lanes of fast traffic in its 58-foot width. Vertical clearance on this level is 13 fect at the curb and 28.7 feet at the center. The lower level carries two interurban railway tracks and has a 31-foot, three-lane pavement for trucks. This section has a vertical clearance of 16 feet.
The Sumner tunnel in Massachusetts is a 5,635-foot toll facility under Boston Harbor. Approached by 63- and 83-foot pavements, it is only 21 feet wide and 12½ feet high. Its 1948 hourly traffic was 3,340 vehicles.
On New Jersey State Route 25 in Jersey City there is a depressed highway covered over for two-thirds of its 3,000-foot length. This semitunnel, with vertical clearance of 14} feet and horizontal clearance of 49 feet, carried 4,550 vehicles hourly in 1948.
At the west approach to the Lake Washington floating bridge in Seattle, there is a 1,466-foot twin-bore tunnel that carried 1,250 vehicles an hour in 1948. Each of the two bores is 23% feet wide and has a minimum vertical clearance of 14½ feet.
Other sizable urban tunnels are the 920-foot Beaucatcher tunnel in Asheville, N. C., and the 931-foot McCallie tunnel in Chattanooga, Tenn. These have horizontal clearances of 32 and 24 feet, and minimum vertical clearances of 14.4 and 20 feet, respectively; their hourly traffic in 1948 was 1,090 and 2,720 vehicles.
The smallest urban tunnel is in the town of St. George, Utah. Less than 500 feet long, it is 21 feet wide and 13% feet high, with an hourly traffic of 585 vehicles in 1948.
Traffic Volumes on the System
Average daily traffic varied in 1948 from less than 200 to more than 70,000 vehicles on various parts of the system. The variation of traffic density throughout the system is shown in figure 3.
MILEAGE CLASSIFIED BY TRAFFIC VOLUME
On 3,518 miles, 36 in urban and 3,482 in rural areas, the traffic averaged between 400 and 1,000 vehicles daily. Carrying between 1,000 and 2,000 vehicles daily there were 9,496 miles, of which 229 were urban and 9,267 miles were rural.
Traffic between 2,000 and 3,000 vehicles daily was served by 8,098 miles of the system, 381 urban and 7,717 rural; and 7,945 miles, of which 834 were urban and 7,111 were rural, served traffic averaging between 3,000 and 5,000 vehicles daily.
Of the sections carrying heavier volumes of traffic, 4,636 miles carried between 5,000 and 10,000 vehicles, 1,874 miles between 10,000 and 20,000, 314 miles between 20,000 and 30,000, and 123 miles 30,000 or more vehicles daily. Of these several traffic volume classes, the mileage of urban and rural routes is as follows:
| Average daily traffic | Urban mileage | Rural mileage |
5,000 to 10,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
1,434 | 3,202 |
10,000 to 20,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
1,207 | 667 |
20,000 to 30,000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
291 | 23 |
30,000 or more . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
119 | 4 |
Total, 5,000 or more . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
3,051 | 3,896 |
In the entire extent of the system there are 1,437 miles, all urban, on which the volume of traffic has not been determined.
SURFACE TYPES AND TRAFFIC VOLUME GENERALLY CONSISTENT
The types of surfaces existing on the system are generally consistent with the volume of traffic. Of the 144 miles of low-type surfaces, 73 miles are on roads traveled by less than 1,000 vehicles daily. Of the 4,990 miles of intermediate-type surfacing, 3,930 miles carry between 400 and 3,000 vehicles daily; and of the 32,642 miles of high-type surface, 29,155 miles are known to carry traffic greater than 1,000 vehicles daily.
Of the 6,947 miles known to carry traffic of 5,000 or more vehicles daily, 6,744 miles are improved with high-type surfaces, and only 200 miles have intermediate-type surfaces; most of the 3-mile remainder is temporarily unsurfaced.
But while there is this general consistency between surface type and traffic volume, inconsistencies are not lacking. For example, there are 33 miles of the system, carrying more than 3,000 vehicles daily, that have only a gravel surface; there are 29 miles that are surfaced with intermediate-type surfaces though their traffic exceeds 10,000 vehicles daily; and there are 119 miles improved with high-type pavements that serve traffic of less than 400 vehicles daily.
INCONSISTENCIES OF TRAFFIC VOLUME AND SURFACE WIDTH
It is in the relation of surface width and traffic volume, however, that the greater inconsistencies appear. On rural sections of the system there are 888 miles of 2-lane surfaces that carried 800 or more vehicles hourly in 1948. Of these, 72 miles are surfaced less than 20 feet wide. In contrast with the grossly inadequate widths of these sections, there are 50 miles of the rural system which, though they carried less than 300 vehicles an hour, are nevertheless improved as divided, multiple-lane highway; and besides these wide divided highways, there are 18 miles of undivided four-lane highway, 152 miles of three-lane, and 3,130 miles of two-lane highway 24 or more feet wide that also carried an hourly traffic of less than 300 vehicles.
The extreme of inadequate width on urban sections of the system is represented by 372 miles of streets less than 22 feet wide, in cities of 5,000 population or more, of which 252 miles are known to have carried more than 300 vehicles an hour.
Fatal Accidents and Deaths
The State highway departments reported 3,603 fatal accidents known to have occurred on roads and streets constituting the designated interstate system in a 1-year period, generally the calendar year 1947. The actual occurrence of fatal accidents was probably somewhat greater, because there are substantial parts of the urban system for which accident data were unobtainable.
For the 31,831-mile rural part of the system the report of accidents is believed to be substantially complete, and the reports indicate that
ACCIDENT RATES
The average rate of fatal accident occurrence on rural sections of the designated interstate highway system was 9.04 per hundred million vehicle-miles. This may be compared with an approximate rate of 9.11 fatal accidents reported for all rural highways in the United States in 1947. However, the accidents on the rural interstate system resulted in fatalities at the rate of 10.94 per hundred million vehicle-miles, whereas the corresponding rate for all rural roads, at 10.66, was slightly lower.
It is apparent that the rural interstate system, in its present state of improvement, is about as safe as, but certainly no safer than, the average of all rural roads, and since its traffic is far above the average in volume, it accounts for an exceptionally large proportion of the annual highway death toll.
RELATION OF ACCIDENT RATES TO LANE WIDTH
On the system as it is presently improved, the fatal accident rate for all two-lane sections was 9.19 per hundred million vehicle-miles. On all three-lane sections, the corresponding rate was 9.08; on undivided four-lane sections, it was 9.41; and on all divided multiple-lane sections, it was 7.65. The superiority of the divided sections from the standpoint of safety is rather marked; the apparently anomalous rate for the three-lane sections possibly results from the fact that these sections carry traffic which in relation to their width is somewhat lower than the similar relation on the existing two-lane roads.
Even the more gratifying rate shown for the existing divided highways is not as low as it might have been had many of these sections been more adequately designed in respect to elements other than their width.
REDUCTION OF ACCIDENTS THROUGH IMPROVEMENT
What a really adequate improvement of the entire system would do to reduce the fatality toll as it stands at present is, of course, a matter of speculation. Some measure of the possibility may be gained from the lower accident rate recorded for portions of the system deemed adequate in their present condition. Of 1,900 miles of the rural system on which this report indicates that no improvement is required, the rate of fatal accidents, known for 1,689 miles, was only 5.65 per hundred million vehicle-miles. Had all parts of the system—its two-, three-, and four-lane sections, divided and undivided—had an accident experience as low in rate as these 1,689 miles requiring no improvement, the fatal accident rate for the whole rural system would have been 5.35 per hundred million vehicle-miles, a reduction of 40.8 percent from the actual rate of 9.04.
At the lower rate there would have been 1,167 fewer accidents and more than 1,400 lives would have been saved in 1 year on the rural sections of the system only.
Appraisal of Current Conditions and Deficiencies
The condition of the existing roads constituting the system having been determined in detail by the several State highway departments, the deficiencies existing were appraised by applying to the determined conditions uniform standards relating to each significant element of design.
ESTABLISHMENT OF STANDARDS
The standards to be applied were previously agreed upon by the Public Roads Administration and a committee of State highway officials appointed by the American Association of State Highway Officials. In general, the standards agreed upon are identical with those adopted by the association August 1, 1945, to govern the design of highways included in the interstate system. In certain respects, however, it was necessary to define more exactly the previously agreed standards in order to facilitate their uniform application for the purposes of this report.
The standards adopted bv the association in 1945 contemplate the provision of design adequate for the service of traffic as it may be expected to develop in a period of 20 years subsequent to the construction of each section of the system as it is improved. This necessitates an estimate of future traffic growth which can be undertaken with reasonable assurance only in the light of specific consideration of the potentialities of each section of the system.
For the purposes of this report such specific consideration has been impracticable. The standards have therefore been applied to all sections of the system in relation to their traffic in 1948. Appraisal of the deficiencies of the existing roads and bridges has been based upon the actual 1948 traffic as reported. The improvements contemplated to eliminate the determined deficiencies, which improvements form the basis of the cost estimates reported, have been planned to serve with adequacy the traffic which it is judged would have used each section of the system, had it been so improved in 1948.
THE STANDARDS APPLIED
The principal standards so applied, both for the determination of deficiencies and the estimation of costs of required improvements, are briefly described here.
Traffic basis
The design shall be such as to accommodate traffic density of the thirtieth highest hour of 1948.
Design speed
Design speed shall be in accordance with the following:
| Miles per hour | ||
| Minimum | Desirable | |
| For rural sections of the system: | ||
Flat topography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
60 | 70 |
Rolling topography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
50 | 60 |
Mountainous topography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
40 | 50 |
For urban sections of the system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
40 | 50 |
Curvature
Curvature shall be related to design speed as follows:
| Design speed | Degree of curvature | |
| Maximum | Desirable | |
70 miles per hour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
4 | 3 |
60 miles per hour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
6 | 5 |
50 miles per hour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
9 | 7 |
40 miles per hour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
14 | 11 |
Stopping sight distance
Applicable to all sections, the road surface ahead shall be visible for distances varying with the design speed as follows:
| Design speed | Stopping sight distance in feet |
70 miles per hour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
600 |
60 miles per hour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
475 |
50 miles per hour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
350 |
Passing sight distance
Applicable to two-lane sections only, the following criteria are to be observed:
- In any 6,000 feet of roadway length, the road surface shall be visible for at least 1,500 feet ahead on a roadway length of at least 1,000 feet.
- The minimum percentage of the length of roadway on which the road surface is visible 1,500 feet ahead shall vary with the density of two-direction traffic in the thirtieth highest hour, as follows:
| Thirtieth highest hour, two-direction traffic | Percentage of roadway length with 1,500-foot visibility of surface ahead |
Less than 500 vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
16⅔ |
500–600 vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
30 |
600–700 vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
60 |
700–800 vehicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
90 |
Gradient
Maximum gradient preferably shall not exceed 5 percent, and in no case shall exceed 6 percent.
Supporting strength
The strength of the road surfaces and foundations shall be adequate for the support of 18,000-pound axle loads in the frequency to be expected.
Right-of-way
Right-of-way width for two-lane rural highways shall preferably be 200 feet, with a minimum of 120 feet. For four-lane rural highways, 250 feet is desirable and 150 feet minimum. For urban highways, right-of-way width will be determined by economic feasibility.
Control of access
Control of access shall be provided where State laws permit and where traffic conditions warrant. Where required, in the absence of permissive State laws, additional right-of-way should be provided sufficient for the construction of frontage roads with controlled access to the through highway.
Lane width
For two-lane rural highways on which traffic density in the thirtieth highest hour is less than 200 vehicles in one direction or 300 in both directions, a minimum lane width of 11 feet is required. For two-lane rural highways of thirtieth-highest-hour traffic density greater than the above, lane width shall be 12 feet.
For rural highways of four or more lanes, lane width shall be 12 feet.
For all urban highways lane width shall be 12 feet.
Divided highways
Divided roadways are required on all highways on which the two-direction traffic volume was 800 or more vehicles in the thirtieth highest hour of 1948. Division may be provided on highways of lesser traffic volume where such provision is less costly than the provision of the required passing sight distance for single two-lane roadways.
The width of median strip on divided highways shall be as follows:
| Width in feet | ||
| Minimum | Desirable | |
Rural highways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
15 | 40 |
Urban highways . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
4 | 12 |
Three-lane highways
Three-lane highways are not permissible.
Shoulder width
In mountainous areas shoulder width shall be a minimum of 4 feet, and elsewhere a minimum of 10 feet, measured to the intersection of shoulder and side-slope planes.
Railroad grade separations
Separation of grades shall be provided at all railroad crossings of two or more main-line tracks, and at all crossings of single main-line tracks on which there are six or more regular train movements daily.
Although by the agreed standards separations are required to be provided at crossings of single main-line tracks of five or less train movements daily only where justified by economic analysis, they were, for purposes of the cost estimate prepared for this report, provided at all such crossings.
Highway grade separations
Separation of grades is to be provided at all highway intersections where the sum of the two-direction traffic volumes on the intersecting roads in the thirtieth highest hour of 1948 was 2,000 vehicles or more, and the lowest volume on any of the roads intersecting was at least 500 vehicles in the same hour.
Bridges
All bridges shall be of steel, reinforced concrete, or masonry construction, and designed for H20-S16 design loading. Bridges include all structures of a length between abutments greater than 20 feet.
Clear height shall be at least 14 feet over the entire width of traffic lanes and at least 12½ feet over the effective shoulder width.
Clear width of bridges of a length of 80 feet or less between abutments shall be equal to the full width of the approach roadway including shoulders.
On bridges of a length greater than 80 feet between abutments, the width between the edge of the pavement and face of curb shall be at least 2 feet and preferably 3 feet. The face of the rail shall be in all cases at least 3½ feet and preferably 4½ feet outside the edge of the pavement.
Sidewalks shall be provided on bridges wherever the volume of pedestrian traffic justifies.
At underpasses, the lateral clearance between the right edge of the pavement of through-traffic lanes and abutments, walls, or piers shall be at least 6 feet. The lateral clearance between the left edge of the pavement and center piers shall be at least 4½ feet.
Deficiencies of Existing Roads and Bridges
When the various conditions existing on the roads, streets, and bridges which presently constitute the designated interstate system are compared with the foregoing defined standards, it is found that a very large mileage of the roads and streets and most of the existing bridges are in some respects inadequate.
MUCH IMPROVEMENT NEEDED
Of the 31,831 miles of roads in rural areas some improvement is required on all but 1,900 miles. Of the 5,969 miles of roads and streets in urban areas all but 398 miles require some improvement. Of the 10,050 bridges carrying rural sections of the system only 483 are completely adequate by the defined standards. The degree of the deficiency of roads and structures in some measure inadequate varies widely, from slight to serious.
SURFACE TYPE DEFICIENCIES
The choice of surface types on the system is reasonably consistent with the volume of traffic carried by the various sections.
Low-type surfaces
The 24 miles unsurfaced and 144 miles surfaced with low-type surfaces are, of course, clearly deficient. A substantial part of these mileages carries traffic in excess of 2,000 vehicles a day. But even on the sections of somewhat lighter traffic, considering that they are part of the country’s major network, low-type surfaces are out of place.
Intermediate-type surfaces
The existing surfaces of intermediate type, found on 4,990 miles of the system, are mostly on sections of relatively low traffic volume.
Only about 91 miles, or about 2 percent, of the total of 4,573 miles of rural roads surfaced with pavement of intermediate type carry as many as 5,000 vehicles per day. Only 568 rural miles, about 12 percent of the total, carry 3,000 or more vehicles a day. The choice of surface for the 91 miles may be seriously questioned; the additional 477 miles carrying traffic between 3,000 and 5,000 vehicles per day may be said to border upon inadequacy.
The situation in the urban areas is less favorable. Of the total of 417 miles of urban sections paved with intermediate types of surface, 26 percent carry traffic of 5,000 vehicles or more daily; 48 percent carry 3,000 or more vehicles a day.
Of the 93 miles with traffic between 3,000 and 5,000 vehicles daily, 27 miles are in towns of more than 5,000 population. At least this mileage and the 109 miles carrying upward of 5,000 vehicles daily are of doubtful adequacy.
High-type surfaces
The bulk of the system, 5,538 miles in urban areas and 27,104 miles in rural areas, is paved with high-type surfaces. On the whole, the choice of pavement type as represented in the existing improvements on the system is appropriate.
Other factors
But a mere classification of surface types does not clearly establish the structural sufficiency of the existing surfaces. Many miles of the surfacing of appropriate type are doubtless of insufficient depth, and the foundation support of a large mileage is probably untrustworthy. The survey that has been made could not, in the limited time available, definitely establish the facts in this regard.
Age of surfaces
The age of the surfaces, previously mentioned, is the best available indication of the probability of a considerable measure of surface inadequacy. The average age of the rural surfaces of all types is 12 years; the average age of roadways on which they are laid is 17 years. Much of the mileage is, of course, of greater age than these averages.
The age of the rural mileage by 10-year groups is shown graphically in figure 4. As this graph also indicates, about 57 percent of the existing surfaces will probably wear out and require replacement in the next 10 years. This projection is based upon a knowledge of the life span of surfaces of all types, gained from a wide study of past surface replacement, and takes into account all of the conditions that contribute to retirement, of which physical deterioration is only one. The same basis underlies the prediction that about 52 percent of the high-type pavements on the system will require replacement by 1959, and that 85 percent of the intermediate-type surfaces and 93 percent of the low-type surfaces will be retired in the same 10-year period.
RATE OF FUTURE IMPROVEMENT
If surfaces of the system are retired in the future at a rate no greater than that of the past, all but the newest and most durable of the now existing surfaces will be replaced in the next 20 years. In view of the more pressing demand for correction of obsolescence already felt and likely to increase in urgency in future years, this is a conservative prediction; but it may serve to set a maximum limit upon the time in which all of the presently recognized deficiencies of the interstate system should be corrected. As the present surfaces are replaced, at least, if at no faster rate, the widths, alinements, sight distances, grades, and all other features of the routes of the system should be brought to the standards recommended in this report as desirable. The building of new surfaces on these routes at any time hereafter without at the same time correcting the serious geometric defects that exist, will be an indefensible prolongation of obsolescence.
DEFICIENCY OF SURFACE AND SHOULDER WIDTH
The present inadequacy of surface width is a much more serious deficiency of the system than the inadequacy of surface type. More than two-thirds of the rural mileage has surfaces that.are too narrow.
Substandard widths on rural roads
The minimum surface width complying with the defined standards under any conditions is 22 feet, and this applies only where the hourly traffic is less than 300 vehicles. The existing surface width is less than 22 feet on 17,746 miles of the system in rural areas, which is more than 55 percent of the total rural mileage. These are not all lightly traveled roads. The hourly traffic volume is less than 300 on only about 9,868 miles of these narrow roads, and is 300 or more vehicles on the remaining 7,878 miles. In fact, about 600 miles of these rural roads with surfaces less than 22 feet wide have hourly traffic volumes of 800 or more vehicles and should be improved as four-lane divided highways.
Surface width of 24 feet is required by the standards for traffic volumes of 300 to 800 vehicles an hour; and multiple-lane divided roads are required for volumes of 800 vehicles or more—four 12-foot lanes for traffic from 800 to 3,000 vehicles, and six lanes for traffic of 3,000 vehicles or more. Three-lane roads and undivided highways of four lanes or more are not desirable and have no place in the standards; however, for hourly traffic volumes of less than 800 vehicles, where two lanes would suffice, they are considered adequate.
Multiple-lane roads needed
On the basis of these standards and the already experienced traffic of 1948, there is a total of about 9,250 miles of the two-lane rural 
Shoulder width
Except in mountainous areas, the defined standards call for shoulder width of 10 feet, measured to the intersection of shoulder and side- slope planes. This is equivalent to an effective shoulder width of about 8 feet. In mountainous areas the standards call for an effective shoulder not less than 4 feet wide. Shoulders effectively 8 feet wide are needed to provide an extra emergency lane into which to turn to avoid a collision. They are needed also as an area in which to stop for the changing of tires or the making of other emergency repairs, and for other similar purposes related to highway safety and the avoidance of obstruction of free traffic flow. More than 71 percent of the rural mileage of the system, 22,684 miles, is without shoulders as wide as 8 feet. On this mileage, parked vehicles must necessarily encroach to a greater or less extent on a traffic lane.
Deficiencies of both pavement and shoulder width
Approximately half of the rural mileage of the system is deficient in both shoulder and surface width. On this mileage, surfaces already too narrow are further constricted whenever a vehicle has to stop for any reason along the way.
Of the entire rural mileage, 5,500 miles at most are adequate in both surface and shoulder width.
Urban width deficiencies
Streets in urban areas should have greater paved widths than rural roads because of the general absence of shoulders and greater frequency of parking. It is, therefore, a startling commentary upon the width of the urban interstate system mileage to find that 2,391 of the 4,141 urban miles for which complete data are available are inadequate in paved width even by the rural road standard.
DEFICIENCY OF CURVATURE
On rural sections of the system there are 3,199 curves of more than 14 degrees, the maximum recognized by the standards as permissible in mountainous areas, and more than half of them are in areas classed as flat or rolling.
There are 15,115 curves, or approximately one every 2 miles on the average, that are sharper than the standard specified as desirable for the type of terrain in which they are located. Of those, 11,182 are sharper than the maximum prescribed by the standards for the desirable design speed; and 6,473 are sharper than the maximum permissible for the minimum design speed suggested for such class of terrain.
DEFICIENCY OF GRADIENT
The standards prescribe an absolute maximum of 6 percent for grades on the system. »There are 668 grades that exceed this limit, 560 on rural, and 108 on urban sections of the system. The aggregate length of these excessive grades is 243 miles, of which about 28 miles are in urban areas.
Grades of 3 to 6 percent
While grades up to 6 percent are permitted by the standards, any grade over 3 percent, if it is long enough, will slow heavy trucks to a speed at which they become annoyingly obstructive of the free flow of lighter traffic. If, under these conditions, the pavement is of two lanes, and especially if passing sight distance is unduly restricted, the obstruction of the heavier vehicles may become dangerous as well as annoying.
Under these conditions a remedy is desirable, and it may be applied by reduction of the grade to a maximum of 3 percent, or by the construction of additional lanes on both sides of the highway, or by the construction of an added lane for slow-moving trucks on the uphill side for at least the distance in which they will be undesirably reduced in speed.
On rural sections of the system there are 5,430 grades of 6 percent or less but more than 3 percent. They aggregate about 2,350 miles in length. Of these, 5,018 grades, totaling about 2,180 miles, are on two-lane or three-lane highways; the remainder are on multilane highways of adequate and inadequate width.
Widening needed on grades
Most of these grades between 3 and 6 percent in steepness are short enough, or exist on roadways wide enough, or for other reasons are acceptable, so that no improvement is required for the correction of a grade deficiency. But 916 of them, totaling more than 400 miles in length, should be widened in some way to abate the nuisance of slow-moving trucks. Of these instances, 592 are on two-lane roads that should be widened on the uphill side for an aggregate distance of about 300 miles by the addition of a truck lane; 284 are on two- and three-lane highways for a total length of 114 miles that require widening to four lanes; and 40 are on multilane highways that require widening. There are only 21 miles in the last category.
Steeper grades
In addition to the above widening necessitated on grades of less than 6 percent, a similar treatment is required on 65 of the grades of 6 percent or more, involving the desirable widening of 26 miles, most of which is now two or three lanes wide.
DEFICIENCY OF SIGHT DISTANCE
Safe stopping distance
Within the 31,831 miles of the rural system there are 21,028 sections, totaling 2,087 miles in length—nearly 7 percent of the total mileage—on which sight distance sufficient to permit safe stopping is not available. All but 1,625 of these sections are on either two- or three-lane roads. The 1,625 sections on multilane highways total 161 miles in length; the two- and three-lane mileage involved is 1,926.
Safe and satisfactory operation on these sections can, in some cases, be provided by the removal of view obstructions such as trees, cut-slopes, and nearby buildings; but in the great majority the alinement or profile of the road, or both, must be changed to flatten horizontal or vertical curves.
Safe passing distance and essential capacity
Passing sight distance is required only on two-way roadways of two and three lanes. Of these categories, on the rural system, there are 29,287 miles, including about 11 miles that are unsurfaced; and of this total, passing sight distance is undesirably restricted on 7,324 miles or about 25 percent. Of the 7,324 miles, 3,968 miles carried an hourly traffic of less than 500 vehicles in 1948. Roads that carried traffic in excess of 800 vehicles hourly aggregate 1,456 miles. The remainder, 1,900 miles, is on roads that carried traffic of between 500 and 800 vehicles an hour.
Correction of deficiencies
Correction of these passing-sight-distance deficiencies can be accomplished in three ways, as follows:
- By improving the alinement and profile of the existing highway. This may involve the relocation of short sections where horizontal curves cause the restriction; or it may necessitate additional excavation at the summit of grades where the restriction is caused by short vertical curvature.
- By constructing another highway that will meet the required standards on a new location.
- By constructing an additional two-lane highway, which with the existing highway will form a divided four-lane highway, on which sight distance of the extent required for safe passing on two- and three-lane roads is not needed.
Of these three means the choice of the most feasible depends on such conditions as the relative adequacy of the surface and other features of the existing road and the present and estimated future traffic.
Conversion to four-lane divided highways
The expenditure of any substantial sum for the lengthening of sight distance on the 1,456 miles that carried hourly traffic of 800 vehicles or more will be wasteful. These roads should be promptly transformed into four-lane divided highways.
Correction of sight-distance deficiencies on the 1,900 miles carrying 500 to 800 vehicles hourly will generally require extensive relocation to develop the alinement needed to provide the sight distance necessary for these roads as two- and three-lane highways. The traffic on these roads is increasing, and in the not distant future may be expected to reach volumes requiring the capacity of divided four-lane highways. When this is done the extended sight distance will not be required. For this reason, the more feasible and perhaps less costly correction in the case of a high percentage of the roads carrying between 500 and 800 vehicles hourly would appear to be early replacement of the existing two- and three-lane roads with four lanes, divided.
Likewise, it may be more feasible to reconstruct to four lanes some of the 3,968 miles now carrying less than 500 vehicles per hour, especially those sections in rough terrain where extensive work would be required to lengthen the sight distance to the required standards.
DEFICIENCY OF INTERSECTION WITH RAILROADS
The defined standards require elimination of all grade crossings of railroads consisting of two or more main-line tracks, and of all crossings of single-track lines on which there are six or more train movements daily.
The 218 remaining crossings of the first category and 542 of the second, a total of 760 crossings, are definitely of sufficient hazard to warrant their elimination.
The need for elimination of the remaining 502 grade crossings of single main-line tracks carrying less than six daily train movements and of the 785 crossings of sidings and spur tracks can be determined only by a careful analysis in each case, giving proper weight to traffic hazard and delay and inconvenience.
Of the 760 grade crossings that definitely should be eliminated, 574 are on urban sections of the system. Only 186 are on rural sections. When these figures are compared with the 1,051 urban and 1,013 rural crossings that already have been separated by the construction of underpass or overpass structures, it is apparent that the work of grade-crossing elimination to date has been much more thorough on the rural than on the urban sections of the system.
DEFICIENCY OF INTERSECTIONS WITH OTHER HIGHWAYS
There are 118 intersections of rural routes of the designated system with other highways at which the combined hourly traffic on the intersecting roads exceeded 2,000 vehicles in 1948, with at least 500 vehicles on the intersecting road of least traffic density. Under these conditions the standards require separation of the grades of the intersecting roads by the construction of overpass or underpass bridges.
In rural areas
It is apparent that the need for this type of improvement on rural sections of the system is not great, and it is encouraging to compare the remaining need of only 118 structures with the 341 similar grade separations already existing.
In urban areas
It is in the urban areas, however, where the greatest need for separation of grade intersection with other streets or highways will exist. This will usually be accomplished by the elevation or depression of the interstate highway for considerable distances. Application of the traffic-volume criterion to the heavy volumes normally present at city intersections would require this in any case, but even where, at particular street intersections, the cross movement may be less than 500 vehicles per hour, the need for greater freedom of flow on the heavy-traffic interstate route is such as to require elimination of the grade intersections anyhow, and in this case the desired end will usually be attained by closure of the unimportant cross streets and diversion of their traffic to nearby separated intersections.
Improvement other than separation
It should be added here, that while on rural sections of the system no great need is found for further separation of highway grade intersections, there is widespread need for the improvement of intersections by other means, such as the lengthening of sight distance, the construction of deceleration and acceleration lanes on the interstate highway, and the construction of channelizing islands to regularize intersecting traffic movements.
DEFICIENCY OF BRIDGES AND TUNNELS
Deficiency of bridge load capacity
The extent of bridge insufficiency has already been generally indicated in the foregoing description of the existing bridges. The defined standards call for load capacity equivalent to that provided by H20-S16 design. The weighing of vehicles now using routes of the system has shown definitely that this standard is none too high for normal civil usage, and it is definitely required in anticipation of possible military needs.
When, at all weighing points, the average weight of all maximum loads occurring with a frequency of at least once daily is found to be 30 tons, and at frequent points throughout the system once-daily-loads reach maxima averaging nearly 62 tons, it is apparent that bridges safely designed for the 36-ton gross vehicle weight on a 28-foot wheel base that is accommodated by the H20-S16 design are a necessity on the system.
On the entire system there are at present only 1,607 bridges of H20-S16 design or rating, of which 1,388 are in rural areas and 219 in urban areas. All other bridges on the system, 8,662 in rura! areas and 1,779 in urban areas, are deficient in some degree in load-carrying capacity by the standard adopted. The deficiency is slight in respect to 2,207 bridges, 1,444 on rural sections of the system and 763 on urban sections, which are rated as of H20 design. All other existing bridges are of definitely inferior strength for the interstate system. The numbers thus deficient are 7,218 in rural areas and 1,016 on urban sections of the system.
Deficiency of bridge clearance
But it is not alone in carrying capacity that the existing bridges are deficient. ‘They are more seriously deficient in horizontal clearance and to some degree in the vertical clearance they provide.
None of the H20-S16 bridges, in either rural or urban areas, is deficient in vertical clearance. However, there are 905 of the bridges of this standard capacity in rural areas that are in some degree inadequate in horizontal clearance. Of these, 627 are substantially inadequate; the remainder are only moderately inadequate. Of the H20 bridges, 18 in rural areas and 4 in urban areas are deficient in vertical clearance; and 1,084 of the bridges of this capacity in rural areas are inadequate in horizontal clearance, 222 of them only moderately so.
It is impossible to rate the adequacy of horizontal clearance for many bridges in urban areas because of uncertainty as to the hourly traffic volume they carried. It is believed that nearly all existing H20-S16 bridges in urban areas are of substantially adequate horizontal clearance. However, more than half of the urban bridges of H20 capacity are seriously inadequate in width.
Of the bridges of capacity inferior to H20, only 53 in rural areas and 10 in urban areas are deficient in vertical clearance. But these bridges, deficient in load-carrying capacity, are also generally deficient in horizontal clearance. Of 7,218 such bridges in rural areas 6,198 are thus deficient, 5,181 of them substantially so.
Deficiency of tunnel clearance
Of the 13 rural tunnels all but one are substantially adequate in vertical clearance, but all are in some degree inadequate in horizontal clearance.
Of the eight tunnels in urban areas, three are deficient in vertical clearance and all are inadequate in horizontal clearance.
Character and Cost of Required Improvements of the System
In the light of the conditions found by the survey to exist on the roads and bridges now constituting the designated interstate highway system, and in consideration of the standards agreed upon as necessary for adequate service of the 1948 traffic on the system, the several State highway departments were asked to determine the kind of improvement that would be required to bring the entire system up to a desirable degree of adequacy, as of the present time, and to estimate the cost of so doing.
As a result of this analysis only 1,900 miles of the system in rural areas and 398 miles in urban areas, as they presently exist, are found to require no improvement. The mileage here classified as urban includes 98 miles in towns of less than 5,000 population. For purposes of the estimate of costs of required improvements, only those sections of the system included within the limits of the urban areas of cities of 5,000 population and more, as defined by the Federal-aid Highway Act of 1944, have been classified as urban. On this basis, the mileage requiring no improvement is 1,998 miles rural and 300 miles urban, a total of 2,298 miles, or about 6 percent of the system as it now exists.
CHARACTER OF ROAD IMPROVEMENT REQUIRED
All other parts of the system are found to require some measure of improvement. The essential improvement of 8,687 miles, about 23 percent of the system as it now exists, consists of widening only. Of this total, 8,306 miles are rural, 381 urban.
Improvements classified as reconstruction, which can be effected with no more than minor relocation of the existing roads, are required on 14,283 miles, nearly 38 percent of the existing total mileage. Of these roads 13,467 miles are in rural areas and 816 miles in urban areas. The most extensive change, improvement which requires complete departure from existing alinement and relocation, is required on the remaining one-third of the system as it now exists. The estimated mileage of the relocated roads is 11,891, which is less than the length of the existing roads by 641 miles; and the total length of the system, 37,800 miles at present, is shortened by this amount to 37,159 miles. Of the 11,891 miles of relocated highways, 9,867 are in rural areas and 2,024 in urban areas.
BRIDGE CONSTRUCTION REQUIRED
On the 11,891 miles of highway relocation proposed, there are 4,893 bridges that would have to be constructed. Of these, 2,693 are on the relocated rural sections and 2,200 are on the urban relocations.
On the sections of the system to be improved on approximately the present locations, totaling 22,970 miles, and on the 2,298 miles otherwise adequate, there are 5,925 bridges which require improvement in some degree, some by outright reconstruction. Of these 5,187 are on rural sections and 738 on urban sections of the system.
TUNNEL CONSTRUCTION
Of the 13 existing rural tunnels, 6 of the least adequate will be avoided in the proposed improvement of the system by relocation of the existing approach roads. The remaining seven, all adequate in vertical clearance, will be supplemented in the proposed improvement by parallel bores. The twin bores, then of adequate width, will each carry one direction of traffic.
Improvement of urban tunnels
Of the eight existing urban tunnels, all but one are proposed for enlargement by the State highway departments. These are the Yerba Buena tunnel in California; the Sumner tunnel in Boston, Mass.; the semitunnel in Jersey City, N. J.; the Beaucatcher tunnel at Asheville, N. C.; the McCallie tunnel in Chattanooga, Tenn.; the tunnel in St. George, Utah; and the Lake Washington tunnel in Seattle, Wash.
The one existing urban tunnel for which no improvement was proposed by the State highway department is the Bankhead tunnel at Mobile, Ala. This tunnel, with its slightly restricted vertical clearance and 21-foot clear width, for an hourly traffic of over 1,000 vehicles in 1948, is regarded by the Public Roads Administration as definitely inadequate. The existing tunnel was built in 1940 at a cost of about $4,000,000. Its inadequacy of width, at least, should be corrected by the construction of a parallel tube, which should provide a minimum vertical clearance of 14 feet. For this purpose an estimate of $5,500,000 has been added to the State highway department’s estimate oft costs.
New tunnels proposed
In addition to the required work of enlargement of existing tunnels, construction of five new tunnels is proposed, of which one is on a rural section of the system and four are in urban areas.
The one new rural tunnel proposed is on U S Route 40 in California at the approach to the Carquinez Strait Bridge.
The four proposed new tunnels in urban areas are a 900-foot tunnel in Louisville, Ky.; a 700-foot expressway tunnel in Boston, Mass.; a 2,400-foot freeway tunnel in Kansas City, Mo.; and a new Palisades tunnel in New Jersey.
TRAFFIC SERVICE OF THE IMPROVED SYSTEM
The 2,298 miles of the system on which no road improvement is required, served in 1948, on the 1,998 rural miles included, an average daily traffic of 4,190 vehicles, and on the 300 urban miles an average of 17,350 vehicles daily. The State highway departments estimate that the 34,861 miles proposed for improvement, if they had been improved as proposed in 1948, would have served on the 31,640 miles of rural sections included an average of 3,450 vehicles, and on the urban sections totaling 3,221 miles an average of 15,360 vehicles daily.
On the basis of these traffic volumes, it is estimated that the system, if it had existed in 1948 in the proposed state of improvement, would have served in that year, on its shortened improved length of 37,159 miles, approximately 62,115 million vehicle-miles of travel. Of this total, 42,380 million vehicle-miles would have been served by the 33,638 miles of rural routes, and 19,735 million vehicle-miles would have been served by the 3,521 miles of urban routes.
These estimates indicate that the system, if it had becn improved as proposed in 1948, would have accommodated on its rural sections, constituting approximately 1 percent of the total rural road mileage, more than 21 percent of the total vehicle-mileage on rural roads. On its sections included within the urban areas of cities of 5,000 population or more, constituting approximately 1 percent of the total city street mileage, it would have served more than 10 percent of the total mileage of urban travel.
COST ESTIMATE OF PROPOSED IMPROVEMENTS
The cost of improvements found to be required has been estimated by the State highway departments on the basis of prices prevailing in 1948. The Federal-aid highway price index for 1948, referred to average prices for the years 1925-29 as 100, was 158.2. Compared with 1940 prices, the average for 1948 was nearly 114 percent higher. Costs of the improvements are, therefore, estimated at high prices; in fact, at the highest prices obtaining for any year in the history of the Federal-aid highway program.
If, in the future, as appears probable, there is some decline from the 1948 price level, the cost of the proposed improvements is likely to be less than the estimate; but no attempt has been made to anticipate the probability in this regard.
Total costs
On the basis of 1948 prices, as stated, the estimated cost of all work proposed on the interstate highway system, as thus far designated, is $11,266,400,000. Of this total, $5,973,000,000 is for improvement of rural sections of the system and $5,293,400,000 is for work proposed on urban sections. The cost of urban improvements is 47 percent of the total.
Widening
Of the $11,266,400,000 total cost, $957,800,000 is for the widening of 8,687 miles of the system as it exists at present, an average of $110,300 per mile. For all rural sections to be widened, a total of 8,306 miles, the cost is $729,300,000, averaging $87,800 per mile. For the 381 miles of urban sections to be widened, the cost is $228,500,000, averaging $599,800 per mile.
Reconstruction
The cost of reconstructing 14,283 miles of the system, involving more than widening but no extended relocation, is estimated at $3,022,700,000, an average of $211,600 per mile. For all rural sections to be reconstructed, a total of 13,467 miles, the cost is $2,117,100,000, averaging $157,200 per mile. For the 816 miles of urban sections to be reconstructed the cost is $905,600,000, averaging $1,109,800 per mile.
Relocation
The cost of relocated sections of the system, aggregating 11,891 miles, is $7,236,700,000, an average of $608,600 per mile. For all rural relocated sections, eeeiing 9,867 rhiles, the cost is $3,077,400,000, averaging $311,900 per mile. For all urban relocated sections, totaling 2,024 miles, the cost is $4,159,300,000, averaging $2,055,000 per mile.
Right-of-way, bridges, and tunnels
All foregoing cost estimates include costs of right-of-way, and of the bridges and tunnels included in the road sections. The estimated cost of right-of-way is $735,000,000 for all rural sections to be improved, an average of $23,200 per mile, and about 12 percent of the cost of the rural sections. For all urban sections the estimated cost totaling $1,667,000,000 averages $517,600 per mile and is more than 31 percent of the cost of the urban sections.
The estimated cost of all bridges to be built or altered on the system is $2,888,900,000. This amounts to about one-fourth of the estimated cost of all work required. Of the total bridge cost, $1,687,200,000, or 58 percent, is for structures in urban areas. New structures to be built on relocated sections of the system represent 72 percent of the total bridge cost.
The estimated cost of all tunnel work proposed is $106,200,000. Of this amount, $82,400,000 is for the enlargement of existing tunnels, of inadequate width. The cost of the five new tunnels to be constructed is estimated at $23,800,000. Of the total cost of tunnels, $46,600,000 is for tunnels in rural areas and $59,600,000 for tunnels in urban areas.
Combined, the estimated costs of right-of-way, bridges, and tunnels amount to $5,397,100,000, which is 48 percent of the estimated total costs. In rural areas, the cost of these elements of the proposed improvements is $1,983,300,000, about one-third of the total rural cost; in urban areas it is $3,413,800,000, which is nearly two-thirds of the total urban cost.
Costs of road construction
After deduction of the costs of right-of-way, bridges, and tunnels, the remainder of the estimated cost, which is the net cost of all road construction, is $5,869,300,000, which represents an average cost of $168,400 per mile for the mileage to be improved. The corresponding cost of road construction work to be executed on rural sections of the system is $3,989,700,000, an average of $126,100 per mile; and for road work only in urban areas the cost is $1,879,600,000, an average of $583.600 per mile.
COST PER MILE
Including all costs, the $11,266,400,000 cost of the work proposed represents an average of $323,180 per mile for the mileage to be improved, and $303,190 per mile for the entire mileage.
Rural and urban costs per mile
The similar total cost for rural sections of the system, $5,973,000,000, represents an average of $188,800 per mile for the mileage to be improved, and $177,600 per mile for the entire mileage, including the 1,998 miles that are adequate in their present condition.
On the same basis, the total cost for urban sections, $5,293,400,000, represents an average of $1,643,400 per mile for the mileage to be improved and $1,503,400 per mile for the entire mileage, including the 300 miles already adequate.
Ratio of rural and urban costs
The cost of the actual work required, on a per-mile basis, appears from the above figures to be about 8.7 times as great for the urban as for the rural sections of the system. On the basis of the total mileage of the system, including the mileage on which no work is required, the per-mile costs of urban and rural work are in the ratio of about 8.5 to 1. COST PER VEHICLE-MILE
If, in 1948, it had been possible to invest in the system the $11,266,400,000 of capital estimated as required for the improvements proposed, that sum could have been raised by a payment of only 18.1 cents for each mile of vehicle travel on the system in that one year. This figure represents the vehicle-mile cost for 1 year's usage only. Vehicle registration and vehicle usage are increasing. In future years the usage of the system, in terms of vehicle-miles of travel on it, will increase. The amount of the probable increase is a matter of speculation.
Future traffic
If traffic using the system in future years is assumed to remain at the level estimated for 1948, the capital cost of the proposed improvement would represent about nine-tenths of a cent per vehicle-mile of the traffic that would be served in a period of 20 years. Since this traffic assumption is very conservative, the computed cost per vehicle-mile is correspondingly conservative. A cost little more than seven-tenths of a cent per vehicle-mile over a 20-year period would probably be a more reasonable measure of the capital burden of the proposed improvements spread over a 20-year period.
Rural and urban vehicle-mile costs
These figures are based on the improvement cost estimated for the system asa whole. For the rural sections only the capital investment would have been repaid by a payment of about 14.1 cents per vehicle-mile of the 1948 traffic, or a maximum of about 7 mills per vehicle-mile in 20 years, a figure that may be reduced in view of the probable traffic increase to less than 6 mills per vehicle-mile.
For the urban system the corresponding vehicle-mile payments and costs are 26.7 cents for 1 year’s traffic; 1.33 cents for the traffic of 20 years continued in the 1948 volume, and probably little more than 1 cent as traffic is likely to develop in a 20-year period.
Comparison of the costs given for the urban and rural sections indicates that the improvement of the urban sections as proposed, in terms of the traffic served, is slightly less than twice as expensive as the proposed improvement of the rural sections.
DATA BY STATES
Table 1 shows the mileage of the system as it is proposed for improvement in the rural and urban areas of each State and the corresponding total mileage; and the estimated costs of improving sections of the system in urban and rural areas of each State and the corresponding percentage of such costs in relation to the respective national total costs.
| State | Mileage of the system, when improved | Estimated total cost of improvements proposed | ||||||||||
| Rural | Percent of total |
Urban | Percent of total |
Total | Percent of total |
Rural | Percent of total |
Urban | Percent of total |
Total | Percent of total | |
Alabama . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
826.2 | 2.46 | 64.6 | 1.83 | 890.8 | 2.40 | $73,306,050 | 1.23 | $14,670,200 | 0.28 | $87,976,250 | 0.78 |
Arizona . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
1,123.3 | 3.34 | 13.6 | .39 | 1,136.9 | 3.06 | 80,579,000 | 1.35 | 11,529,000 | .22 | 92,108,000 | .82 |
Arkansas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
476.5 | 1.42 | 41.3 | 1.17 | 517.8 | 1.39 | 58,752,400 | .98 | 19,536,800 | .37 | 78,289,200 | .69 |
California . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
1,714.2 | 5.10 | 186.3 | 5.29 | 1,900.5 | 5.11 | 552,672,000 | 9.25 | 616,755,000 | 11.65 | 1,169,427,000 | 10.38 |
Colorado . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
627.1 | 1.86 | 34.6 | .98 | 661.7 | 1.78 | 39,175,883 | .66 | 33,117,640 | .62 | 72,293,523 | .64 |
Connecticut . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
163.3 | .49 | 99.1 | 2.82 | 262.4 | .71 | 63,596,000 | 1.06 | 155,706,000 | 2.94 | 219,302,000 | 1.95 |
Delaware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
22.9 | .07 | 2.6 | .07 | 25.5 | .07 | 25,019,500 | .42 | 24,409,000 | .46 | 49,428,500 | .44 |
Florida . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
1,012.6 | 3.01 | 128.6 | 3.65 | 1,141.2 | 3.07 | 63,137,100 | 1.06 | 52,125,400 | .98 | 115,262,500 | 1.02 |
Georgia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
1,027.3 | 3.05 | 83.3 | 2.37 | 1,110.6 | 2,99 | 103,148,750 | 1.73 | 72,578,835 | 1.37 | 175,727,585 | 1.56 |
Idaho . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
608.2 | 1.81 | 8.7 | .25 | 616.9 | 1.66 | 46,773,000 | .78 | 3,470,000 | .07 | 50,243,000 | .45 |
Illinois . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
1,314.1 | 3.91 | 226.8 | 6.44 | 1,540.9 | 4.15 | 321,168,042 | 5.38 | 535,209,461 | 10.11 | 856,377,502 | 7.60 |
Indiana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
906.0 | 2.69 | 159.4 | 4.53 | 1,065.4 | 2.87 | 139,233,570 | 2.33 | 250,203,840 | 4.73 | 389,437,410 | 3.46 |
Iowa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
640.5 | 1.90 | 29.7 | .84 | 670.2 | 1.80 | 68,935,700 | 1.15 | 9,413,000 | .18 | 78,348,700 | .70 |
Kansas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
672.8 | 2.00 | 28.7 | .82 | 701.5 | 1.89 | 71,698,390 | 1.20 | 18,085,000 | .34 | 89,783,390 | .80 |
Kentucky . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
578.8 | 1.72 | 69.6 | 1.98 | 648.4 | 1.74 | 100,534,698 | 1.68 | 81,398,001 | 1.54 | 181,932,699 | 1.61 |
Louisiana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
470.7 | 1.40 | 126.4 | 3.59 | 597.1 | 1.61 | 89,065,900 | 1.49 | 131,944,000 | 2.49 | 221,009,900 | 1.96 |
Maine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
277.8 | .83 | 22.6 | .64 | 300.4 | .81 | 43,740,000 | .73 | 30,431,000 | .58 | 74,171,000 | .66 |
Maryland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
219.8 | .65 | 45.7 | 1.30 | 265.5 | .71 | 140,493,484 | 2.35 | 101,784,296 | 1.92 | 242,277,780 | 2.15 |
Massachusetts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
176.8 | .53 | 159.0 | 4.52 | 335.8 | .90 | 112,783,600 | 1.89 | 339,112,500 | 6.41 | 451,896,100 | 4.01 |
Michigan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
894.1 | 2.66 | 68.4 | 1.94 | 962.5 | 2.59 | 181,335,450 | 3.04 | 235,063,700 | 4.44 | 416,399,150 | 3.70 |
Minnesota . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
766.9 | 2.28 | 83.6 | 2.37 | 850.5 | 2.29 | 58,395,501 | .98 | 103,115,543 | 1.95 | 161,511,044 | 1.43 |
Mississippi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
569.3 | 1.69 | 121.7 | 3.46 | 691.0 | 1.86 | 62,017,800 | 1.04 | 26,122,000 | .49 | 88,139,800 | .78 |
Missouri . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
1,032.8 | 3.07 | 38.0 | 1.08 | 1,070.8 | 2.88 | 133,579,990 | 2.24 | 101,704,000 | 1.92 | 235,283,900 | 2.09 |
Montana . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
1,217.4 | 3.62 | 26.3 | .75 | 1,243.7 | 3.35 | 108,507,450 | 1.82 | 8,097,000 | .15 | 116,604,450 | 1.03 |
Nebraska . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
453.9 | 1.35 | 6.7 | .19 | 460.6 | 1.24 | 40,869,000 | .68 | 7,370,000 | .14 | 48,239,000 | .43 |
Nevada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
526.3 | 1.56 | 11.0 | .31 | 537.3 | 1.45 | 17,940,300 | .30 | 1,628,000 | .03 | 19,568,300 | .17 |
New Hampshire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
169.0 | .50 | 32.0 | .91 | 201.0 | .55 | 26,910,00 | .45 | 13,419,00 | .25 | 40,329,000 | .36 |
New Jersey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
90.3 | .27 | 102.1 | 2.90 | 192.4 | .52 | 59,703,300 | 1.00 | 344,350,100 | 6.51 | 404,053,400 | 3.59 |
New Mexico . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
989.7 | 2.94 | 22.8 | .65 | 1,012.5 | 2.72 | 52,257,000 | .87 | 5,852,700 | .11 | 58,109,700 | .52 |
New York . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
962.3 | 2.86 | 72.0 | 2.04 | 1.034.3 | 2.78 | 643,146,000 | 10.77 | 219,135,000 | 4.14 | 862,281,000 | 7.65 |
North Carolina . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
637.0 | 1.89 | 75.7 | 2.15 | 712.7 | 1.92 | 42,993,000 | .72 | 29,864,000 | .56 | 72,857,000 | .65 |
North Dakota . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
478.8 | 1.42 | 19.5 | .55 | 498.3 | 1.34 | 29,365,120 | .49 | 15,785,600 | .30 | 45,150,720 | .40 |
Ohio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
999.8 | 2.97 | 216.6 | 6.15 | 1,216.4 | 3.27 | 396,185,000 | 6.63 | 362,406,000 | 6.85 | 758,591,000 | 6.73 |
Oklahoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
734.4 | 2.18 | 45.7 | 1.30 | 780.1 | 2.10 | 136,767,500 | 2.29 | 29,650,000 | .56 | 166,417,500 | 1.48 |
Oregon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
675.2 | 2.01 | 27.8 | .79 | 703.0 | 1.89 | 94,450,000 | 1.58 | 23,465,000 | .44 | 117,915,000 | 1.05 |
Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
1,025.9 | 3.05 | 331.0 | 9.40 | 1,356.9 | 3.65 | 528,013,000 | 8.84 | 398,566,000 | 7.53 | 926,579,000 | 8.22 |
Rhode Island . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
23.4 | .07 | 25.2 | .72 | 48.6 | .13 | 6,082,000 | .10 | 79,925,976 | 1.51 | 86,007,976 | .76 |
South Carolina . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
604.5 | 1.80 | 92.5 | 2.63 | 697.0 | 1.88 | 39,425,750 | .66 | 80,143,000 | 1.51 | 119,568,750 | 1.06 |
South Dakota . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
499.5 | 1.48 | 15.2 | .43 | 514.7 | 1.39 | 40,196,800 | .67 | 4,638,000 | .09 | 44,834,800 | .40 |
Tennessee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
967.2 | 2.88 | 77.7 | 2.21 | 1,044.9 | 2.81 | 172,634,734 | 2.89 | 69,022,782 | 1.30 | 241,657,516 | 2,15 |
Texas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
2,573.0 | 7.65 | 191.8 | 5.45 | 2,764.8 | 7.44 | 286,833,400 | 4.80 | 149,104,200 | 2.82 | 435,987,600 | 3.87 |
Utah . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
672.3 | 2.00 | 31.8 | .90 | 704.1 | 1.89 | 61,208,300 | 1.03 | 23,045,000 | .44 | 84,253,300 | .75 |
Vermont . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
311.4 | .93 | 28.4 | .81 | 339.8 | .91 | 47,508,220 | .80 | 6,910,300 | .13 | 54,418,520 | .48 |
Virginia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
844.6 | 2.51 | 57.1 | 1.62 | 901.7 | 2.43 | 170,536,000 | 2.86 | 36,773,000 | .69 | 207,309,000 | 1.84 |
Washington . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
521.0 | 1.55 | 58.5 | 1.66 | 579.5 | 1.56 | 118,363,500 | 1.98 | 66.096,600 | 1.25 | 184,460,100 | 1.64 |
West Virginia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
165.7 | .49 | 46.2 | 1.31 | 211.9 | .57 | 94,514,500 | 1.58 | 112,095,000 | 2.12 | 206,609,500 | 1.83 |
Wisconsin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
424.4 | 1.26 | 24.7 | .70 | 449.1 | 1.21 | 75,025,050 | 1.26 | 52,178,950 | .99 | 127,204,000 | 1.13 |
Wyoming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
949.0 | 2.82 | 23.7 | .67 | 972.7 | 2.62 | 54,309,750 | .91 | 5,759,910 | .11 | 60,069,660 | .53 |
District of Columbia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
16.6 | .47 | 16.6 | .04 | . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
180,670,000 | 3.41 | 180,670,000 | 1.60 |
National total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . |
33,638.0 | 100.00 | 3,520.9 | 100.00 | 37,158.9 | 100.00 | 5,972,936,482 | 100.00 | 5,293,435,334 | 100.00 | 11,266,371,816 | 100.00 |