There’s A Trend To Raise Speed Limits, But It Increases Risk Of Death And Serious Injury

Getting to a destination as fast as possible is often a driver’s goal, but it’s frequently not the safest choice. So raising posted speed limits, which is on the upswing in the United States, may do little to save time and increase traffic flow, but could lead to more crashes, injuries, and deaths.

Those are the key findings of a new study released on Thursday by the AAA Foundation for Traffic Safety, a nonprofit research and education association.

“The movement in statehouses to raise speed limits is happening across the country in at least eight states this year,” Jennifer Ryan, director of state relations for AAA, said in a statement. “But the benefits are overrated, and the risks are understated. Increasing speed limits does not always yield the positive results envisioned by traffic planners.”

The report follows new data released on Monday by the National Highway Traffic Safety Administration (NHTSA) during the launch of its annual “Speeding Wrecks Lives” prevention campaign that calls attention to how speeding is a critical factor in vehicle crashes nationwide and makes up almost one-third of all traffic deaths.

Speeding fatalities reached a 14- year high in 2021. More than 12,000 people were killed in speeding-related crashes that year, and another almost 330,000 people are estimated to have been injured.

For the study, AAA Foundation researchers examined 12 roadway sites of various types, each with a new posted speed limit— six raised and six lowered. Some highlights:

• Raising posted speed limits was associated with increased crash frequencies and rates for two of the three Interstate Highways assessed;
• Lowering posted speed limits was associated with decreased crash frequencies and rates for one of the two principal arterials; and
• Changes in travel times were small in response to both raised and lowered speed limits.

“Our study analyzed before-and-after data on a dozen roadways that raised or lowered posted speed limits and found no one-size-fits-all answer regarding the impact of these changes,” David Yang, president and executive director of the AAA Foundation, said in a statement. “However, it is critical to consider the safety implications when local transportation authorities contemplate making changes with posted speed limits.”

The study also found that the likelihood of speed limit violations increased after posted speed limits were lowered. Better public awareness education when speed limits are set or changed is among the recommendations suggested by the AAA Foundation.

The new study is the association’s third examining the effect of posted speed limit changes on safety. In the first study, traffic engineers were asked how posted speed limits are set and what factors they consider in changing them. Crash testing in the second study indicated that small speed increases have severe and potentially deadly effects on crash outcomes.

The AAA Foundation’s recent results are consistent with other research, which shows that when speed limits are raised, speeds go up, as do fatal crashes, according to the Insurance Institute for Highway Safety. “High speeds make a crash more likely because it takes longer to stop or slow down. They also make collisions more deadly because crash energy increases exponentially as speeds go up,” the safety group noted. “Raising speed limits leads to more deaths. People often drive faster than the speed limit, and if the limit is raised they will go faster still.”

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