Unveiling the Potential Risks Associated with America's Speed Limit Calculations on Road Safety

In a significant change of pace, states across the nation are reconsidering the traditional approach to setting speed limits. The debate, which has gained traction in recent years, involves a reevaluation of the long-standing 85 percent rule and a focus on context and safety.

For decades, the 85 percent rule has guided speed limits, determining the limit by studying free-flowing traffic and identifying the speed at or below which 85 percent of vehicles travel. This figure is then rounded to the nearest five miles per hour. However, the Associated Press reports that the federal government has clarified that the 85% figure was never intended to be a rule, but rather a guide.

Despite this, many states continue to adhere to the simplicity of the old system. Yet, critics argue that the 85 percent rule is outdated and unsafe. They contend that it fails to account for factors such as crash data, land use, and pedestrian activity, which can significantly impact road safety.

Safety advocates argue that the 85 percent rule creates a self-reinforcing cycle: people drive faster, the limit gets raised to match, and roads become more dangerous for pedestrians, cyclists, and drivers. This perspective has led to a growing movement advocating for context- and safety-based approaches to setting speed limits.

Some states and cities are already shifting away from the 85 percent rule. For instance, Seattle saw a decline in serious injuries after lowering neighborhood limits to 20 mph. Similarly, Madison, Wisconsin, is implementing a "20 is Plenty" campaign, lowering the speed limit to 20 mph in many residential areas. Ohio now allows municipalities to consider the slower 50th percentile speed in busy pedestrian areas.

Boulder, Colorado, authorities say the old rule did little to reduce speeds, suggesting that street design may be more important than the number on the sign. Wide lanes, sweeping curves, and long sightlines invite higher speeds, regardless of the posted speed limit.

The National Highway Traffic Safety Administration (NHTSA) has joined the debate, urging drivers to slow down. The NHTSA's stance underscores the growing consensus that speed limits should reflect how roads are built to be driven, a viewpoint shared by driver advocates.

The shift towards context-based speed limits is not without controversy. Some argue that this approach could lead to inconsistent speed limits, creating confusion for drivers. However, proponents of the change contend that prioritising safety over speed will lead to a more equitable and safer road network for all users.

As the debate continues, it is clear that the traditional approach to speed limits is under scrutiny. The future of speed limits may lie in a more nuanced understanding of road safety, one that takes into account the unique characteristics of each road and the communities they serve.