Safety Corner, August 2021

John Allen


Massachusetts is famous, or perhaps notorious, for its rotary intersections. Some date back to the construction of Metropolitan District Commission (now Department of Conservation and Recreation) parkways in the early decades of the 20th Century. A few rotaries are recent and apply the design elements of the modern roundabout, with deflection at entries and exits to slow traffic.

Rotaries are well-known to achieve smoother traffic flow and greater throughput than signalized intersections, but there are also disadvantages. Motorists’ yielding to pedestrians at crosswalks is on the honor system, and there is often not enough honor.  Also, with no traffic signals to organize traffic into platoons, the wait can be long when turning from a side street onto a street which leads away from a rotary

Be glad that you are a bicyclist rather than a pedestrian as you approach a rotary. Negotiating for the best lane position on entry to the rotary makes travel through the rotary easy. Unless you are leaving at the first exit, go to the inside. In a single-lane rotary, control the lane or even merge toward its left to allow motorists to exit on your right. In a two-lane rotary, you want to be in the inside lane until you approach your exit. Traffic is slower at the inside, because the curve is sharper, and no vehicles will cross your path, because there are no exits at the inside. You must yield to traffic in the rotary when entering it. Be careful that entering traffic is yielding to you as you exit.

The video embedded below illustrates the basic principles, at a small rotary in Waltham. My friend, CyclingSavvy student Ian Whiting, recorded the video in a course where I was one of the instructors, this past May.  If you are interested in checking this out where the rubber hits the road, I plan to have another course in the fall.


John S. Allen is CRW Safety Coordinator, a certified CyclingSavvy Instructor and League Cycling Instructor and author of Bicycling Street Smarts.