How Communities Balance Speed and Safety on the Roads

Speeding and distracted driving continue to be major issues in most states. The National Highway Traffic Safety Administration estimates that more than 20,000 people died in motor vehicle crashes in the first half of 2022, on top of nearly 43,000 highway deaths in 2021.

These staggering statistics have led many cities and states to impose traffic calming measures, including lowering speed limits, radar speed signage, installing bike lanes and more. Unfortunately, while these steps have proven to be effective in slowing traffic and resulting traffic fatalities, they have also incurred the wrath of daily commuters who complain that it is taking much longer to get to and from work.

How Did Speeding Become Such a Problem?

Part of the problem with excessive speeding–and the inevitable crashes and fatalities that occur–is that for nearly 60 years, departments of public works and transportation have relied on the 85th percentile rule. Created at a time when the nation’s highway system was still young, cars drove at slower speeds, and research on traffic safety didn’t exist, the 85th percentile rule is based on the 1964 “Solomon Curve,” which states simply that speed limits should be set at what 85% of drivers think is healthy. As a result, state and local governments seeking to accommodate motorists’ behavior focused on increasing capacity and minimizing delays set speed limits based on this rule, even in the face of rising community demands for more stringent measures to reduce speeding.  

With the benefit of hindsight and data identifying speed as the overlooked factor in the mounting number of traffic fatalities, a 2017 report by the National Transportation Safety Board recommended revising the traditional approach to setting speeds by balancing the 85th percentile rule with a safe systems approach that incorporates factors such as crash history and the presence of vulnerable road users such as pedestrians and bicyclists.  

Since that time, elected officials, transportation engineers, police and professional advocates have felt emboldened to declare that “no loss of life is acceptable” on our streets and highways. And while that approach has ushered in several measures designed to lower speeds, it has also exacerbated the complaints of commuters demanding to get to their destination as quickly as possible.

Creating a Balance Between Safety and Speed

So, is it feasible to think that a balance can be struck between safety and speed? If the past few years have shown us anything, it is the impossibility of continuing to raise travel speeds while simultaneously trying to create a safer road system. Common traffic calming measures like installing speed cameras along high-risk areas like school zones and popular pedestrian and cycling routes, and the construction of roundabouts, can reduce severe crashes by as much as 78%.

Similarly, road diets can be used to convert an existing four-lane divided roadway into a three-lane roadway consisting of two thru lanes and a center two-way left turn lane. An overall crash reduction of up to 47% can be achieved by using road diets to reduce rear-end and left-turn crashes. A road diet also represents a low-cost safety solution when planned in conjunction with a simple pavement overlay. While both measures, improve roadway safety they also slow the speed of traffic.

However, there are other traffic calming initiatives that can substantially increase safety without radically reducing the speed of commuter traffic. Installing high-friction surface treatments, better known as rumble strips, can reduce wet road crashes by 52% and curve crashes by 24%, while enabling commuter traffic to maintain a reasonable rate of speed. Similarly, backplates–dark silhouettes added to a traffic signal which isolate the signal face from signs, sunlight and other environmental conditions–can improve the visibility of the signal’s illuminated face by introducing a controlled contrast background reducing crashes by 15%, all without substantially slowing traffic flow.

Where new construction or major improvements are being considered, auxiliary turn lanes for left or right turns provide physical separation between turning traffic that is slowing or stopped, while simultaneously allowing thru traffic to continue. Installation of turn lanes can reduce total crashes by up to 48% for left-turn lanes and up to 26% for right-turn lanes, without drastically reducing the speed limit.  

Another option that represents a compromise between increasing safety and providing an easier commute for workers is the reversible roadway system some cities, such as Washington, D.C., employ. On these roads, one or more lanes switch directions to add capacity inbound to downtown in the mornings and outbound to the suburbs in the evening. These streets typically are marked with two sets of double-yellow lines, one solid and one dashed. The dashed lines are to be followed during the rush hour periods when the lanes are reversed.

While this approach can be effective for drivers who regularly use these designated roadways, it can be a nightmare for drivers who are unfamiliar with the process. As a result, safety advocates have usually lobbied against their use.

The bottom line here is that something must give. While workers understandably want their commute to be as fast as possible, their safety and the safety of pedestrians, cyclists and others are simply too important to be ignored. State and local governments must focus on compromise, recognizing that what works on one road system doesn’t necessarily work on all systems. By taking the time to research and evaluate what design, engineering and enforcement would be most effective, governments can strike the appropriate balance between safety and the need to move traffic quickly and efficiently.