States Revise Speed Limits by Driver Behavior

The Debate Over Speed Limits and the 85% Rule

Rose Hammond, an 85-year-old resident of northwest Ohio, has been tirelessly advocating for years to lower the 55 mph speed limit on Mitchaw Road. This two-lane road passes through her assisted living community, a church, two schools, and a busy park that serves as a hub for youth sports leagues. Her frustration stems from the frequent sight of motorcycles speeding by, which she believes poses a serious threat to public safety.

"What are you waiting for, somebody to get killed?" she asked officials, emphasizing the urgency of the issue. Amid growing public pressure, Sylvania Township requested a review of the speed limit in March. The surprising outcome was that the current 55 mph limit is actually 5 mph too low, according to county engineers. This revelation highlights the complex history behind how speed limits are set in the United States.

The practice of setting speed limits based on the 85% rule dates back to studies conducted on rural roads in the 1930s and 1940s. This rule suggests that the posted speed should reflect the 15th-fastest vehicle out of every 100 traveling on a road, rounded to the nearest 5 mph increment. However, this approach is now being questioned as some states, with support from the federal government, seek to modify or replace it when determining local speed limits.

The 85% Rule and Its Limitations

The 85% rule assumes that the safest speed is the one most drivers naturally choose, creating a balance between safety and practicality. However, critics argue that this approach can lead to a feedback loop where drivers feel encouraged to speed, resulting in higher speed limits over time. Jenny O’Connell, director of member programs for the National Association of City Transportation Officials, points out that this method can inadvertently prioritize speed over safety.

In response, the association developed an alternative approach called "City Limits," which focuses on minimizing risks for all road users. This model considers factors such as street activity levels and the likelihood of conflicts like collisions. Advocates argue that the 85% rule is based on outdated research and does not account for the modern urban environment, where streets are often more dynamic and populated.

The Federal Highway Administration recently updated its guidelines, signaling that the 85% rule is not a strict requirement but rather a suggestion. It encourages communities to consider factors such as pedestrian risk and crash frequency when setting speed limits. While some states have embraced this shift, others still rely heavily on the 85% rule due to its simplicity and familiarity.

Changes in Practice and Public Safety Efforts

Several cities have taken steps to implement new approaches. Madison, Wisconsin, launched the "20 is Plenty" campaign, lowering speed limits on residential streets to 20 mph. Similarly, Seattle saw a decline in serious injury crashes after reducing speed limits in a pilot program. These changes demonstrate the potential benefits of rethinking traditional speed limit practices.

California, known for its strict adherence to the 85% rule, has also seen some shifts. Recent legislation allows local governments to deviate from the rule if they can prove a safety need. However, advocates for pedestrians and bicyclists argue that these changes are not enough to address the broader issues of road safety.

On the other hand, Jay Beeber, executive director for policy at the National Motorists Association, defends the 85% rule, stating that it helps minimize speed variations among drivers. He argues that setting unrealistic speed limits could lead to unfair enforcement and confusion among drivers.

The Impact of Speed Limits on Safety

High-speed highways have long been a focus of debate, especially as speed limits continue to rise. North Dakota recently became the ninth state to allow 80 mph on certain highways, while Texas has a 40-mile stretch where 85 mph is permitted. A 2019 study by the Insurance Institute for Highway Safety found that increasing speed limits leads to higher fatality rates, particularly on interstate highways.

Chuck Farmer, vice president for research at the institute, noted that modern vehicles make it harder for drivers to gauge their speed accurately. "You're in a cocoon," he said, highlighting the dangers of high-speed driving.

Despite these concerns, the situation on Mitchaw Road remains unchanged. Ohio law sets maximum speeds for different types of roadways, regardless of what the 85% rule suggests. However, the state is gradually evolving its approach, giving more weight to roadway context and allowing cities to reduce speed limits based on the 50th percentile speed when there is a significant presence of pedestrians and bicyclists.

Looking Ahead

While changes are slowly taking shape, the future of speed limit policies remains uncertain. For residents like Rose Hammond, the wait for meaningful action continues. She expresses frustration with the lack of progress despite years of advocacy.

"It's hard not to get discouraged," she said. As states and communities continue to reassess their approach to speed limits, the goal remains clear: to create safer roads for all users.