Page:America's Highways 1776–1976.djvu/351

 By the late 1950’s, an increasing number of miles of freeways were being put into operation. Because very little was known about freeway lighting with respect to driver behavior and safety, the Bureau and the Connecticut State Highway Department undertook in 1959 a comprehensive field study on the effect of illumination and delineation. Nine different conditions of illumination and delineation were studied. No significant difference with respect to vehicle speeds, lateral position, and clearances between vehicles under the nine study conditions were noted. In general, it appeared that some benefit resulted from full-level illumination in the deceleration area and that even greater benefit occurred when illumination was combined with roadside delineation. Since then HRB has reported a number of similar studies which generally corroborate the original findings. As a result of these research conclusions, recent lighting installations have been largely located at interchanges and other points of conflict or decision.

The photolog system is a sequential set of photographs, usually taken at one-hundreth mile increments and recorded on a continuous film strip, of the highway and its immediate environment. Each photograph normally provides the viewer with the date it was made, the route, milepoint, and direction of travel, but it can include other data as well. Photologging was developed more or less on the “let’s try it and find out” method by research and operations engineers. Today it is an operational tool in some 40 States. The varied uses to which photologs may be applied include evaluating the adequacy of traffic control devices, providing information for project design, identifying and evaluating high accident locations, acquiring planning inventory data and supplying data for research studies.

The basic principle of highway safety, as summarized by Thomas H. MacDonald in 1949 in Public Roads magazine, is that maximum safety is provided by designing, building and operating the highway and vehicle to fit the driver’s known capabilities and limitations. This concept recognizes the tremendous variation in age, ability, experience, skill and physical and mental condition of tens of millions of drivers. It prescribes that the highway and the vehicle should accommodate the maximum amount of this variation and assist the maximum number of drivers in their task. It has been the foundation for nearly all useful and productive research in highway safety.

Since the 1930’s, many studies have provided the bases for safer design criteria for highways and vehicles. The highway safety research has included on-highway experiments and observational studies of passing practices, lane position, braking and acceleration capability, grade-climbing ability, and other aspects of driver behavior and vehicle performance.

Research studies over the past several decades have shown that the most effective way to facilitate the driver’s task is to provide him with a highway having full control of access. Such a highway, best exemplified by the Interstate Highway System, prohibits 345