The traffic shown for the existing highways is that which actually used them in 1937. Had these roads been thoroughly modernized throughout, it is conservatively estimated that their traffic would have been from 15 to 30 percent greater than it actually was.
FUTURE INCREASE OF TRAFFIC
Based upon estimates of probable future changes in population, in the number of motor vehicles per capita, in motor fuel consumed per vehicle, and upon an estimate of the increase in miles traveled per gallon of fuel by the average vehicle as a result of improvements in motor vehicles and changes in driving habits, plate 22 shows a predicted trend in the vehicle-mileage of travel on all rural roads.
It is assumed that the rate of increase in vehicle-miles of travel onmain highways will exceed the average rate of increase on all rural roads because: (1) A faster rate of development of abutting properties is anticipated for main roads than for local roads; and (2) the average length and number of long trips (50 miles or more) is expected to increase at a faster rate than the average length and number of shorter trips. The allowance for each of these factors depends, of course, upon the specific section of highway considered.
In considering an allowance for the first of these factors for the selected system composed of three east-west and three north-south routes, it must be remembered that access is assumed to be denied to all abutting property owners except at designated poimts where approach facilities are provided. This condition restricts development of abutting property to areas close to access points. Where the selected route is located in such manner that it provides an attractive connection between such areas and nearby marketing or metropolitan areas, a very fast rate of development may be anticipated. However,
