BOISE – For drivers in search of shorter commutes, higher speed limits and speeding in general may seem like a solution. But according to new research by the AAA Foundation for Traffic Safety, the risk of traveling at faster speeds likely outweighs the rewards.
AAA examined 12 roadway sites across America with recent changes to their posted speed limits – six raised and six lowered – to compare the results before and after the change. Raising posted speed limits was associated with increased crashes on two of the interstate highways that were analyzed, while lowering speed limits resulted in fewer crashes in several of the cases that were examined.
“Faster speed limits may be seen as a way to improve traffic flows, but our research shows that the argument isn’t very compelling,” says AAA Idaho public affairs director Matthew Conde. “You’d have to travel 100 miles to save roughly five minutes by driving at 80 MPH instead of 75 MPH. Meanwhile, faster speeds require greater stopping distance and more time to reach a safe impact speed. The elevated risk of a violent crash, serious injury, or death simply isn’t worth it.”
In previous AAA research, impact speeds from a 40-MPH crash showed a relatively low risk of injury. But at 56 MPH, sensors on the test dummy recorded a 67% increase in the likelihood of facial fractures, neck trauma, and severe brain injury, and much higher potential for leg fractures as well.
“So, it isn’t just about how fast you are going – it’s about reading the road, weather, and traffic conditions to make sure you have enough space to slow down,” Conde said. “That means that each road situation is unique, and circumstances may change on the same road throughout the day. Through the Safe Systems approach, traffic engineers can factor human error, vehicle performance, the road design, and other important variables into the equation, boosting safety in the process.”
Not surprisingly, when speed limits were raised, the number of traffic violations decreased, while the opposite happened when speed limits were lowered. Many safety organizations now feel that the traditional practice of using the 85th percentile (the speed at which 85% of drivers are traveling) shouldn’t be the sole or deciding criterion for setting speed limits.