Techniques for reducing crashes at multilane roundabouts

By Saumya Jain

While roundabouts overall are much safer for motorists compared to traditional intersections, they also introduce new crash opportunities. This is especially true for cases where there are multiple lane options after entering the circle. In this month’s ITE Journal, transportation experts from Canada and U.S. explain why multi-lane roundabouts can trigger new types of crashes and address countermeasures to improve safety.

Multi-lane roundabouts introduce several types of crashes that are not possible at single-lane roundabouts. The most common are two sideswipe crashes, left-turn, and merge-type crash. These often occur when a driver in the left-lane makes an exit from the circle, while there is another driver in the right-lane intending to continue into the circle. As explained in the article, the determination of who is at fault depends on the crash type and on who entered the circle first. This highlights the main problem: a gap in guidelines and on-site instructions for multilane roundabout usage. This challenge has been highlighted in previous research and current analysis conducted by the authors. Without the right signage and directions, user perceptions greatly vary on lane usage, merging, and yielding. Additionally, reducing the number of lanes in the roundabout would be the most effective safety measure for motorists.

Diagram of ways to design roundabouts
Figure 1 Possible geometric and signage countermeasures (Source: ITE Journal)

Even with safety improvements, roundabouts in the U.S. are still comparatively unsafe for cyclists and pedestrians. European nations and the United Kingdom offer lessons in improving roundabouts for all road users. One such example is a newly proposed, Dutch-inspired roundabout that prioritizes cyclists and pedestrians over motorists by forcing the latter to reduce speed and yield for active travelers. To learn more, watch this video from local authorities.

Photo credit: Kelly Lacy