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.
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