While writing these words, my smile continues to broaden. As someone who’s spent the last 25 years analyzing, designing, defending, and driving roundabouts, this is a great week to pause and feel the joy of National Roundabouts Week. It feels like we’re finally getting it. Not just fellow traffic engineers; but our families, friends, and the broader public. Much of the controversy has faded, including many of the less-informed comments at public meetings, in coffee shops, and on the streets. Now roundabouts are winning (even though they always have been). They—the great equalizer of traffic control—are saving lives, improving operations, and making our communities a little better. (OK, maybe a lot better).
As our communities continue to evolve and expand, so do the challenges of managing traffic flow and ensuring safety on our transportation systems. The modern roundabout has become a strategic ally in the battle to improve conditions. Often praised for their effectiveness in both intersection control and safety enhancement, roundabouts offer myriad benefits that make them a preferred intersection design choice. Even a quick review makes it clear as to why roundabouts are a commendable form of intersection traffic control, thanks to their exceptional safety and operational efficiency.
Safety First
One of the primary reasons roundabouts have gained popularity is because of their ability to substantially enhance safety. Traditional signal-controlled intersections are more prone to crashes due to factors such as red-light running and high-speed collisions. Roundabouts, on the other hand, mitigate these risks in several ways.
- Reduced Speeds: Roundabouts inherently enforce lower speeds, reducing the severity of collisions and giving drivers more time to react to unexpected situations. The relative speed differential among all vehicles in a roundabout and on intersection approaches is negated as motorists are all traveling at similar, consistent speeds.
- Elimination of High-Speed Right-Angle Collisions: Unlike signal-controlled intersections, where vehicles often collide at high speeds from perpendicular directions, roundabouts eliminate the possibility of these dangerous collisions. While crashes can still occur at roundabouts, they are often the minor fender-bender type.
- Fewer Conflict Points: Roundabouts significantly reduce the number of potential conflict points, making intersections less complex and decreasing the likelihood of crashes. Roundabouts benefit from good geometry, exhibiting only a fraction of the troublesome crash patterns typical of right-angle intersections. A typical four-legged intersection has 32 vehicle-to-vehicle conflict points and 24 vehicle-to-pedestrian conflict points. By comparison, a four-legged roundabout has only eight vehicle-to-vehicle conflict points and eight vehicle-to-pedestrian conflict points. This results in roundabouts providing an approximate 70 percent reduction in conflict points.
- Directional Traffic Flow: With roundabouts, vehicles move in a single direction, minimizing the chances of head-on collisions. The images below show a conflict-points comparison of a standard 2-lane intersection vs. a single-lane roundabout.
Studies have consistently shown that roundabouts lead to a substantial reduction in both the frequency and severity of crashes, making them a superior choice for promoting safety. Roundabout intersections have been shown to reduce fatality crashes by 90%, severe injury crashes by 75%, and all crashes by 50%.
Operational Efficiency
Beyond safety, roundabouts also offer notable operational advantages that contribute to the overall efficiency of traffic flow.
- Continuous Traffic Flow: Roundabouts facilitate a continuous flow of traffic, minimizing the need for vehicles to come to a complete stop, thus reducing congestion and idling times.
- Minimal Delay: Traditional intersections often lead to significant delays, especially during peak hours. Roundabouts distribute traffic more evenly, resulting in shorter wait times and improved travel times.
- Capacity and Scalability: Roundabouts can handle varying traffic volumes and can be easily scaled up or down as needed. This adaptability is particularly useful for areas experiencing changing traffic patterns such as intersections near schools, special events, or construction-related detours.
- Fuel Savings and Emissions Reduction: Reduced idling and smoother traffic flow translate to lower fuel consumption and decreased emissions, contributing to a greener environment.
Pedestrian and Cyclist Safety
Roundabouts aren't just beneficial for vehicle traffic; they also prioritize the safety of pedestrians and cyclists.
- Dedicated Crossings: Roundabouts feature designated crosswalks with refuge islands, allowing pedestrians to cross one direction of traffic at a time.
- Slower Vehicle Speeds: The reduced speeds within roundabouts make interactions between vehicles and pedestrians/cyclists safer and more manageable.
Summary
As communities (both rural and urban) strive to optimize traffic control and enhance safety, the roundabout stands out as an exceptional solution. By virtue of its inherent safety features, operational efficiency, and consideration for pedestrians and cyclists, the roundabout model showcases its ability to alleviate traffic congestion, reduce crashes, and promote a more seamless flow of vehicles. By embracing the advantages of roundabouts, communities can create safer, more efficient intersections that cater to the needs of all road users.
So, let’s keep the momentum going. Educate your families, your neighbors, and your friends on the overall greatness of the mighty roundabout. There’s soon to be more coming to a location near you. After all, round really is better. #RoundisBetter
For more information on National Roundabouts Week (September 18-22, 2023), visit: https://safety.fhwa.dot.gov/nrw/.
Lonnie Burklund, PE, PTOE, is a professional transportation engineer and leads the Traffic & Technology Department at JEO Consulting Group.