The regulating agencies, in their turn, had to improvise, to try one scheme and then another, to back-track—in short, had to learn how to do a job that had never been done before. The success of this joint effort is evident in the statistics of wartime travel.
MOTOR-VEHICLE REGISTRATIONS AND TRAVEL DURING THE WAR PERIOD
During the 20-year period just preceding World War II motor-vehicle registrations and traffic increased steadily, except for a slight, temporary dip during the depression years. The increase from 1921 to 1941 was more than threefold for registrations and approximately sixfold for vehicle-miles of traffic. In figure 10 the trends in population, registrations, and vehicle-mileage from 1921 to 1948 are shown, with 1940 as the base year.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/00/Highway_Needs_of_the_National_Defense_-_Figure_10.png/400px-Highway_Needs_of_the_National_Defense_-_Figure_10.png)
Decline of traffic
In 1941 highway traffic increased at an accelerated rate, because of the abnormal activity preceding our entry into the war. Almost im-