Do Higher Speed Limits Result in More Fatal Crashes?
By Autumn Cafiero Giusti
A new study linking higher speeds to tens of thousands of fatalities is reigniting the debate as to whether raising the speed limit makes highways more dangerous or actually safer.
The study claims that although fatality rates fell during this period — mainly due to safer vehicles — rates would have been much lower if not for increases in speed limits.
"Speeding remains one of the biggest safety problems that we have on our roads," says IIHS spokesman Russ Rader. "And states are making that worse."
The national maximum speed limit was implemented in 1974 and required that states adopt 55 mph as their maximum speed limit in order to receive federal highway funds. Congress relaxed the restriction in 1987, allowing states to increase speed limits to 65 mph on rural interstates.
Since the law's repeal in 1995, 38 states have set speed limits of 70 mph or higher on some portion of their roadways, according to the National Conference of State Legislatures. A handful of states raised the interstate speed limit to 80 mph.
A portion of Texas Highway 130 just east of Austin and San Antonio has an 85 mph speed limit making it the highest maximum limit in the nation.
"States have been on a tear to increase speed limits," Rader says. "And this study doesn't take into account the increases of the last three years."
Kara Macek, spokeswoman for the Governors Highway Safety Association, says the results from the IIHS study don't come as a surprise.
"It's pure physics," she says. "As you go up in speed, the likelihood of you surviving a crash goes down astronomically."
Macek contends that people don't treat speed limits as limits. They generally drive 5 to 10 mph faster than the posted speed limit, regardless of how high it is.
"The definition of a limit is the maximum," she says. "But people treat it as the minimum.”
Making the case for higher speed limits
Some observers of highway trends argue that raising the speed limit can actually reduce highway accidents and lower fatalities. John Bowman, spokesman for the National Motorists Association, contends speed limits almost always increase simply because they were artificially set too low to begin with.
And when limits are set at the correct levels, the traffic flow evens out and accidents tend to decrease.
Bowman cites National Highway Traffic Safety Administration figures as evidence of his theory. Fatalities per 100 million vehicle miles traveled have dropped almost every year since the repeal of the speed limit law in 1995. In 1994 and 1995, there were 1.73 fatalities per 100 million vehicle miles traveled.
In 2014, the most recent year measured, the number stood at 1.09 fatalities per 100 million vehicle miles traveled. That's a 37 percent decrease in nearly two decades.
Enforcing laws regarding driving speeds
Rader and Macek say the solution to the highway fatality problem is for state and local law enforcement to focus more on enforcing existing speed limits, whether that means placing officers with speed guns on the side of the road or implementing automated enforcement measures, such as speed cameras.
"We should be vigorously enforcing the speed limits that we have, not raising them," Rader says.
Macek says this kind of enforcement forces drivers to change their behavior.
"If people think they're going to get caught, they will drive more slowly," she says.