Page:America's Highways 1776–1976.djvu/128



In 1920 the Bureau of Public Roads began a series of “transportation surveys” in cooperation with the States, and in a few instances, with counties and cities as well. In all, there were 16 investigations extending over a period of 16 years. Twenty States were involved at various times with the BPR in the studies.

The first surveys were essentially traffic censuses to help the cooperating States select their 7-percent Federal-aid systems. Gradually, the studies became more and more research-oriented, and by 1925 the BPR and the States were looking into every aspect of highway transportation: the ownership of motor vehicles; the seasonal, monthly and daily variations in traffic; the types of vehicles using the roads; the origin and destination of cargoes; the size and weight of trucks and the kinds of tires they ran on, and whether they were overloaded. In the later studies, they examined driver behavior—the average speeds of drivers traveling freely on the highway and their observance of traffic laws, such as those prohibiting passing on hills and curves.

Maryland State Roads Commission testing laboratory. Core drilling outfit taking test cores.

In Maine, the researchers discovered a historical relationship between vehicle ownership, population and traffic. By projecting historical trends ahead, they were able to make fair estimates of traffic 5 years in the future. From these predictions, the investigators placed the highways in priority groups according to traffic density, the amount of future truck traffic, and need for improvement. Finally, they suggested improving the deficient mileage to an adequate standard for the 5-year future traffic, financing the improvements with either a bond issue or an increase in the gasoline tax. Following the Maine study, this 122