Page:Highway Needs of the National Defense.pdf/110

 Appendix I.—SIZES AND WEIGHTS OF VEHICLES

It has already been shown, in figure 10, that the war proved to be only a temporary interruption to the long-term upward sweep of traffic volumes and that by 1946 the 1941 peak had been exceeded and by 1948 the volumes were about what would have been indicated by a projection forward of the prewar trend. The year 1941 was one of intense preparation for the war, and highway activity was at un- precedented levels, yet traffic volumes in 1948 were 18 percent higher, as can be seen from table 3, and this in spite of the fact that new auto- mobiles had been scarce and costly since the war. These increases took place on all classes of roads and in all sections of the country. By classes of road, and by sections of the country, the increases of 1948 traffic over 1941 traffic were as follows:

Figure 16 shows, for the three sections of the country, the traffic for the year ending with each month from 1942 to 1948, inclusive, as a percentage of the traffic in the calendar year 1941. For example, during the 12-month period ending March 1948, traffic in the eastern section was about equal to that of the calendar year 1941, while in the central regions it was 14 percent higher and in the western regions 27 percent higher than 1941 traffic.

The postwar increase in trucking has been even more rapid. As can be calculated from table 8, the ton-mileage hauled in 1947 exceeded that of 1941 by 25 percent. Preliminary figures indicate that 1948 ton-mileage exceeded the 1941 figure by about 37 percent.

INCREASES IN AXLE LOADS

As previously mentioned and shown in figure 15, the trend toward increased frequency of heavy axle loads has continued unabated into the postwar period. For each 1,000 trucks, there were six times as many axle loads weighing 18,000 pounds or more, seven times as many weighing 20,000 pounds or more, and seven times as many weighing 22,000 pounds or more in 1947 as in the 1936-38 period when the prewar weighings were made. But this does not tell the whole story. Truck traffic volume in 1948 was approximately double that of 1936, and preliminary figures indicate that the frequency of heavy axle loads was at least as great as in 1947. A road carrying 600 trucks per day in the earlier year would have had, on the average, eight axle loads daily weighing 18,000 pounds or more, three weighing 20,000 pounds or more, and only one weighing 22,000 pounds or more. Assuming an average traffic increase, this same road in 90