Maine residents have surely noticed new speed limit signs on Interstate 95, which went up recently. In many places where the speed limit was once 65 mph, the maximum is 70 mph and, north of Old Town, 75 mph. Speed limit increases also have been made on parts of I-295, I-195 and I-395.
It would be natural for one to think increasing speed limits would heighten the risk of crashes and fatalities. Indeed, if done without concern for driving habits and road conditions, it could. The trick is to determine the speed at which most drivers are already traveling and then devise speed limits around the realities of the road.
The 5-mph increase will, in all likelihood, do very little to change driving habits.
National research has found it advisable for states to base speed limits on the “ 85th percentile speed,” which is how fast 85 percent of vehicles are traveling, regardless of posted limits. It may be amended based on road environment, crash history and engineering judgment.
The concept is based on the rationale that the large majority of drivers are reasonable, do not want to crash, and want to get where they’re going quickly. The drivers who travel at speeds in the lower 15 percent are considered unreasonably slow, and those above 85 percent are assumed to be traveling at an unsafe speed.
Posting a speed below the 85th percentile speed penalizes many reasonable drivers, and national research shows most of them do not change their speeds anyway to match speed limits they believe are unfair. Also, lower speed limits don’t necessarily make people safer.
In a study of driver behavior in 22 states completed for the Federal Highway Administration and the U.S. Department of Transportation, researchers found that crashes at 58 sites where speed limits were lowered increased 5.4 percent. Meanwhile, crashes at 41 sites where speed limits were raised decreased 6.7 percent.
The likelihood of being in a crash is highest when people are traveling at speeds that are far lower or far higher than most other drivers.
Hence, the new speed limits.
The new limits probably won’t make the road any more dangerous or safe, and they probably won’t make people drive any faster or slower.
The simple fact is that the change probably won’t change much. If anything, it will benefit reasonable drivers and encourage police to penalize major speed violators, rather than average motorists. Drivers out there in the 85th percentile should consider the change a validation of their driving habits.