When the National Maximum Speed Limit in the United States was repealed in November 1995, twelve states almost immediately increased their rural interstate speed limit (early change states). Another eleven states increased their rural interstate speed limit after the first quarter in 1996 (late change states), while the remainder of the states did not increase their limit during 1995 or 1996 (no change states). The effect of the speed limit changes on rural interstate fatality and injury rates was examined using a mixed ANOVA design weighted by vehicle miles, with year (1994 to 1996) as a within-subjects variable and the timing of the speed limit change (early change, late change or no change) as a between-subjects variable. Fatality and injury rates did not change significantly from 1994 to 1996 for any of the groups or overall. However across all three years the fatality and injury rates of the no change group were significantly lower than the two groups that increased their speed limit. That is, prior to the speed limit change the groups that increased their speed limit had a poorer road safety record than the no change group and this difference continued after the change. (A)
Abstract