Roundabouts have become a popular alternative to traditional intersections, for good reason. Roundabouts have multiple benefits for our communities. They are safer than traditional intersections—they result in slower vehicle speeds and consequently, fewer and less severe collisions. They also reduce carbon emissions and result in lower maintenance costs than traditional intersections. However, deficiencies in roundabout design can result in a poor experience for the user. In order for communities to realize the benefits roundabouts can bring, it is imperative for roundabouts to be designed properly.
This can pose a challenge, as roundabouts cannot be designed from a template—they require plenty of flexibility in design to balance the varying needs of the project. Each intersection location is different: traffic volumes, right-of-way, skewed alignments, and many more factors can all vary significantly. Because much of roundabout design is dependent on the judgement of the designer and not easily gained from guides, a roundabout designer needs to have in-depth knowledge of roundabout design, as well as the specific needs of the project.
As part of the South Carolina Local Technical Assistance Program Webinar Series, I hosted an in-depth discussion on roundabout design checks. While each roundabout project is unique, there are several key principles a designer should keep in mind:
- Provide adequate vehicle capacity and traffic lanes.
- Maintain speed control and speed consistency.
- Accommodate design vehicles.
- Accommodate all modes of transportation.
- Create natural driving paths.
- Maintain sightlines.
- Achieve positive guidance.
Above all, flexibility in the design process is essential. Roundabout design goes beyond what you can learn through a template or guidebook, and engineering and design judgement is critical. Often, competing objectives will need to be weighed and balanced to achieve an effective solution. Mead & Hunt has designed many successful roundabout projects nationwide. Through this extensive experience, we have learned what to look for and what to avoid to design a roundabout that will work for each community’s unique needs. As always, designing solutions that put people first is at the forefront.
