tances, and even for distances up to 250 miles, has attained enormous proportions. Highways have been rebuilt at immense expense in order to be capable of conducting such traffic. Thus, many of the trunk lines of highways in the United States have passed into an economic position analogous to that of the railways of the country, but with the difference that while the highways have been built and are maintained largely at the public expense, the state taxes levied on automobiles furnish only a small part of the cost of con- struction and maintenance, and even so the chief part of such taxes are paid on account of pleasure automobiles and relatively little for the commercial vehicles that carry the heaviest loads.
This introduces a complicated economic problem, which was discussed lucidly by Philip Cabot in the Atlantic Monthly for August, 1921. It is a serious question whether the transportation of freight for anything more than short distances, or in competition with the steam railways, be not an economic waste if all things be taken into account, including the cost of building and maintaining the highways. Without going further into this complicated question, it seems to me, however, that in the enumeration of the national wealth some entry must now be made for the investment in highways.
There is no complete inventory of the roads of the United States. The Bureau of Public Roads, Department of Agriculture, has a document, now out of print, giving the estimated mileage of roads in 1914, and its figures together with the estimated construction from 1914 to the end of 1920 are shown in the following table:
