Outdated rule that lets drivers set speed limits on US roads could be changing amid spike in highway deaths

For years, 85-year-old Rose Hammond has pleaded with officials in northwest Ohio to lower the 55 mph speed limit on Mitchaw Road — a busy two-lane stretch that passes her assisted living community, a church, two schools, and a park filled with children playing sports.

“What are you waiting for, somebody to get killed?” she asked, frustrated by the daily roar of speeding motorcycles and a lack of official action.

In response to public pressure, Sylvania Township asked county engineers in March to study whether the speed limit should be lowered. The result was unexpected: by traditional standards, the speed limit was actually 5 mph too low.

That conclusion stems from a long-standing method used to set speed limits — the 85th percentile rule. Developed from traffic studies in the 1930s and 1940s, it recommends setting speed limits based on the speed at or below which 85% of drivers naturally travel in free-flowing conditions.

This approach, still widely used across the U.S., assumes that drivers intuitively choose safe speeds. But critics say it’s outdated and problematic.

“The problem with this approach is it creates a feedback loop,” said Jenny O’Connell of the National Association of City Transportation Officials. “People speed, and then the speed limits go up to match that speed.”

To address this, her organization developed “City Limits,” an alternative method that factors in how streets are used, including the presence of pedestrians, cyclists, and potential crash risks. It’s part of a growing effort to rethink speed management in urban areas.

Even the Federal Highway Administration has stepped in. In a recent update to its traffic control manual — the first since 2009 — the agency clarified that the 85th percentile rule is not a binding requirement and encouraged local governments to consider broader safety factors like crash history and pedestrian activity.

Safety advocates say it’s a step in the right direction, though not a complete fix.

“The 85th percentile should not be the Holy Grail,” said Leah Shahum, director of the Vision Zero Network. “But too often, it still is.”

Some cities are already taking action. Madison, Wisconsin is lowering residential speed limits from 25 to 20 mph as part of its “20 is Plenty” campaign. Seattle saw similar safety improvements when it implemented lower speeds in a pilot program, including a 7% reduction in 85th percentile speeds and fewer serious crashes.

California, a longtime proponent of the 85% rule, has recently loosened rules to allow local governments more flexibility if they can demonstrate a clear safety need. But change has been slow.

“There’s still a mindset that cars come first,” said Kendra Ramsey of the California Bicycle Coalition.

Still, not everyone supports moving away from the traditional model. Jay Beeber, policy director at the National Motorists Association, argues that the 85th percentile remains the safest approach.

“Drivers respond to how a road feels,” Beeber said. “It’s unfair to build a road that encourages 45 mph speeds and then post it at 30 mph just to issue tickets.”

Meanwhile, speed limits on highways are increasing. Since the federal government repealed the national 55 mph cap in 1995, many states have raised limits. North Dakota recently became the ninth state to allow 80 mph. Texas even permits 85 mph on one stretch between Austin and San Antonio.

But higher speeds bring higher risks. A 2019 study from the Insurance Institute for Highway Safety found that every 5 mph increase in maximum speed limits raises fatal crash rates by 8.5% on interstates and 2.8% on other roads.

Back in Sylvania Township, officials want to lower the speed limit on Mitchaw Road — ideally to 40 mph or less. But Ohio law sets maximum speeds by road type, and for now, the 55 mph limit remains in place.

Still, the state is evolving. Ohio recently allowed cities to use the 50th percentile speed — the median speed — to set limits when there’s a high presence of pedestrians and cyclists. The state is also consulting experts to align with modern trends in road safety.

“People are living and moving differently than they did 40 years ago,” said Michelle May, Ohio’s highway safety program manager. “We want to prioritize safety.”

But for Rose Hammond, it’s hard to stay hopeful after years of trying.