OBJECTIVES AND SCOPE

The objective of this research was to determine the effects of raising and lowering speed limits on driver behavior and reported accidents for nonlimited access rural and urban highways. Driver behavior effects included the speed distribution, mean speeds, speed variance, percent of drivers exceeding the speed limit, and close following behavior. The safety effects icluded total accidents, severe accidents, and multivehicle and single vehicle crashes.

The scope of the study included the collection of speed and accident data in 22 States, as shown in figure 1, at 100 sites where speed limits were altered and at 100 comparison sites. Repeated speed measurments were made at 14 selected sites to examine the short- and long-term effects of speed limit change. A sample of eight adjacent routes was also selected to examine the indirect effects of speed limit change on nearby roadways.

[Figure 1]

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