mileage of these is very small indeed when viewed in the light of a nationwide highway program.
However, information on the costs of toll roads, and of free roads of comparable design, is sufficient to permit engineers in the field to make estimates of the cost of constructing the various portions of the Interstate System and of other routes as toll roads, which should be reasonably accurate on the average. Information is also available on the volumes of traffic using all the principal roads throughout the Nation as a result of continuing studies made by the State highway departments in cooperation with the Bureau of Public Roads. This traffic volume information is insufficient, in itself, to determine the traffic that would use a toll road, but it may be interpreted, in the light of the results of intensive traffic studies made before and after the construction of several of the existing turnpikes, to form a basis for reasonable estimates. Such estimates, while certainly not sufficiently accurate for use in the final appraisal of individual projects, are believed, when combined for several sections or routes, to provide a fairly reliable general measure of toll-road feasibility.
For the purposes of this study, estimates were made of construction costs and traffic volumes for all sections of the Interstate System, exclusive of sections already adequately improved and those known in 1954 to be scheduled for early improvement either as toll or free roads. Traffic was forecast for the years 1964, 1974, and 1984. General rates of traffic increases assumed were consistent with those rates used in the report, Needs of the Highway Systems, 1955–84, recently submitted to the Congress (84th Cong., 1st sess., H. Doc. No. 120).
Similar estimates were made for those routes not on the Interstate System but believed to have toll potential. All of the State highway departments cooperated fully in this undertaking by providing the basic cost and traffic data from which toll feasibility was calculated.
Estimates made by the States were carefully reviewed and compared. Revisions were made in a few instances for consistency or where indicated as proper on the basis of additional information. While these revisions were substantial in certain cases, they were not such as to make appreciable differences in the broad, overall determinations.
Basic assumptions
The costs and traffic estimates were used to determine the probable extent of toll-road feasibility. Certain basic assumptions had to be made.
First, it was assumed that the financing would be by revenue bonds, which is the method for most of the toll roads now being built. In keeping with current toll-road financing practices and experience on existing toll roads, the following values were assigned to the various items entering into the calculations:
- (a) Amount of bonds: 1.12 times construction cost.
- (b) Term of bonds: 40 years.
- (c) Rate of interest: 3.5 percent.
- (d) Toll rate, passenger cars: 1.75 cents per vehicle-mile.
- (e) Toll rate, trucks: 4.00 cents per vehicle-mile.
- (f) Revenues from concessions: 7 percent of gross receipts from tolls.
- (g) Administrative, operational, and maintenance costs, and replacement reserve: 20 percent of gross revenues.
