Effect of the 65 m.p.h. speed limit on highway safety in the U.S.A. (with comments and reply to comments)

Since April 1987, 40 states have increased their speed limits on rural Interstate highways to 65 m.p.h. Motorists have responded by driving faster on these highways and some evidence suggests they are driving faster on highways without a change in speed limits as well. Both the average speed and the 85th percentile in speeds has increased on roads posted at 65 m.p.h. Various statistical approaches for estimating the effect of these higher speeds indicate that fatalities on highways posted at 65 m.p.h. were 15 to 25% higher than expected in 1988.