And state police patrol resources were then decreasingly available for such safety programs as truck inspections and drunk-driving checkpoints. Furthermore, many drivers who wanted to speed switched to less traveled, less patrolled but less safe roads. The 55 mph limit may have decreased fatalities on some roads by increasing patrolling and decreasing traffic volume from what it would have been without that limit. However, the effect on a state's total highway system was apt to be a net subtraction from safety. Raising speed limits lured some drivers back to safer, more heavily patrolled roads, and allowed highway patrols to shift resources back to the programs they thought most effective.
Many collisions occur when cars are overtaking and passing one another.
Speed variance among drivers increases when speed limits are set so low that there is a high rate of noncompliance. When in November 1995 Congress empowered states to set such limits as they chose, fatalities did not increase the 10 percent to 14 percent predicted by the Cassandras who foresaw 4,400 to 6,000 extra deaths per year. Neither did fatalities increase even the 2 percent to 3 percent that would have been expected, extrapolating from recent trends. This is a cautionary tale about the complexity of discerning reality in a welter of statistics. It also is an encouraging tale.