Roundabouts offer safe, efficient intersection systems that keep communities moving. But despite their benefits, the U.S. has mostly excluded their use in modern transportation designs—until recently. We spoke with Denver Regional Leader Noah Nemmers to learn why roundabouts are making a comeback and why municipalities should make the switch.
Why are there so few roundabouts in the US?
Up until the last decade or so, the U.S. hadn’t adopted roundabouts for a few reasons.
When roundabouts were first introduced in the early 1900s, the designs lacked the regulation and efficiency of today’s versions, which resulted in unnecessary congestion and accidents. In addition, their multi-lane layouts took up considerable space in urban areas, making them a less practical solution.
As electricity gained popularity across the country, traffic signal salesmen convinced cities that lights were a safer, more modern approach to improving intersections. Traffic lights became the standard.
However, decades of traffic studies now provide clear and conclusive data: modern roundabouts dramatically outperform signalized intersections in both safety and efficiency. This irrefutable evidence has led to a revival of roundabout design across the country and helped usher a roundabout-first mentality.
What are the benefits of roundabouts?
The U.S. is now replacing traffic signals at a rate of 500-700 a year due to several compelling roundabout benefits:
Safety: The Data Speaks for Itself
- Crash Reduction: Modern roundabouts reduce total crashes by almost 50% compared to signalized intersections. At higher-speed rural intersections, crash reductions can reach much higher percentages.
- Injury Crash Reduction: Injury crashes drop by up to 80% after conversion to roundabouts.
- Fatality Reduction: Most strikingly, roundabouts reduce fatal crashes by up to 90%. To put that in context for every 10 fatalities at a signalized intersection, a roundabout could save nine lives—or even all lives in many cases.
- Pedestrian Safety: Pedestrian injury rates are reduced by up to 75%, thanks to lower vehicle speeds and fewer conflict points.
Traffic Flow
Continuous movement eliminates unnecessary stops which helps improve congestion. Studies by IIHS and other agencies show that roundabouts can increase intersection capacity by 30-50%.
Environmental Impact
With less idling roundabouts help lower emissions and overall fuel consumption. Roundabouts often reduce pavement area and offer more opportunities for landscaping. Vehicles travel at slower, steadier speeds, resulting in less engine revving and braking noise.
Cost Efficiency
Converting a traffic signal intersection into a roundabout does have upfront construction costs, but this investment cuts down on long-term maintenance and energy needs. Traffic lights require ongoing upkeep (especially after damaging storms) and their lights consume electricity 24/7.
Community Beautification
Creative engineers are using the centers of roundabouts to bring more visual interest into their communities. Art installations, waterfalls, gardens, and other unique features help enhance entryways and commercial properties.
“I am passionate about building roundabouts. They’re fun to design. Especially when retrofitting an existing intersection, there are many unique challenges to solve; I love finding ways to shrink the footprint and bring communities more efficiency. Plus, once you get used to driving in them, you’ll really notice how frustrating it is to sit at traffic lights.”
– Noah Nemmers
Roundabouts project support
Whether you’re building a roundabout from scratch or converting an existing intersection, partnering with the right team makes all the difference in bringing these benefits to life.
At V3, our multidisciplinary approach simplifies the process. Our cohesive team of civil engineers, surveyors, environmental specialists, and construction management professionals tackle challenges from all angles to find the best possible solutions.
Plus, our strategic partnerships with local agencies ensure projects meet all necessary guidelines to continue moving forward.
We offer:
Design & Engineering
- Dual-lane and single-lane roundabout design using advanced tools like Rodel and TORUS for performance modeling
- Geometric design with over two decades of roundabout experience
Surveying & SUE
- Topographic mapping, boundary surveys, and subsurface utility engineering to ensure minimal disruption and accurate ROW planning
Environmental & Drainage
- Stormwater and water quality design, including grade-separated crossings and ADA-compliant pedestrian features
Construction Support
- Phased construction plans to reduce community impact, including temporary lane shifts and flagging strategies
- Bid and construction administration to streamline project delivery
- Construction Management to ensure that the project is delivered as designed, on time, and within budget.
To learn more about roundabouts and how we can support your project, connect with our team.