How to Stop Worrying and Learn to Love the Roundabouts

By Maria Bakali and Benjamin Grant
June 25, 2014

Comment received at the Ocean Beach Implementation Project Open House on May 10, 2014. Photo by Shannon Fiala.​


SPUR is leading a transportation study at Ocean Beach to further develop the access and circulation recommendations of the Ocean Beach Master Plan. The transportation design team had proposed a new solution for Skyline Boulevard: a series of carefully designed "modern roundabouts." This proposal will improve safety and streetscape aesthetics while maintaining a constant flow of vehicle traffic at moderate speeds.

What is a modern roundabout?
Modern roundabouts allow for removing traffic signals from intersections. Vehicles slow down and yield, but do not necessarily stop, on entry. This keeps a steady and efficient traffic flow, saving time and fuel.


The modern roundabout. Photo courtesy Caltrans.

The modern roundabout is a  specific type of intersection and should not be confused with the rotary (a large circular highway interchange common in the Northeast) or the neighborhood traffic circle (a small circle used for traffic calming in residential areas). 

The advantages of the modern roundabout
Research conducted by the Insurance Institute for Highway Safety in partnership with the Federal Highway Administration shows that roundabouts perform better in terms of safety than conventional intersections, resulting in:

  • 76 percent reduction in injury
  • 90 percent reduction in fatal crashes
  • 35 percent reduction in general collisions

Roundabouts substantially improve pedestrian safety, with 40 percent fewer pedestrian collisions than traditional intersections. These impressive reductions may be attributed to lower motor speeds, shorter pedestrian crossings and the considerable decrease in conflict points between vehicles as well as with pedestrians.

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Modern roundabouts combine safe crossings with efficient traffic movement. Diagram coutesy the Federal Highway Administration.

Roundabouts eliminate left turns across pedestrian crosswalks, right-angle crashes and head-on collisions. The striking safety benefits combined with increased time savings — up to 89 percent — and reduced greenhouse gas emissions have turned many roundabout skeptics into enthusiasts​. Initial design and construction costs are also offset by low maintenance expenses when compared to intersections with signals. On top of that, the centers of roundabouts can support trees, vegetation and public art and perform stormwater management.

How popular is the modern roundabout?
Roundabouts were not very common in the American landscape, but they began increasing in number a few years ago. According to the Federal Highway Administration, approximately 150 to 250 roundabouts are built in the United States annually. From Delaware and Maryland to Utah and California roundabouts are used more and more as a traffic management tool.

San Francisco has only one modern roundabout, built very recently on Otis Street in Mission Bay. Roundabout skeptics argue that U.S. drivers’ unfamiliarity with roundabouts is going to increase confusion and create difficulties in adjusting their travel behavior to navigate them properly. Studies prove the opposite and, once constructed, roundabouts gain overwhelming public support.

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Roundabouts are everywhere in the US from Delaware (top) to our own backyard in Mission Bay (bottom). Photo from Google maps. 


Why would roundabouts be the best solution for Skyline?
SPUR’s Ocean Beach transportation project team envisions a series of roundabouts on Skyline to transform today’s intersections from dangerous and inhospitable to safer and more attractive, as shown here at Sloat and Skyline. Diagram by AECOM.

Intersections on Skyline today are dangerous and at times impossible to cross on foot or bike. The roundabout design proposal is a more rational approach that clarifies these massive and complex intersections, in particular the one at Sloat Boulevard. A group of roundabouts work well in sequence, and they can offer a better transition from the fast, semi-rural Skyline Boulevard into shared city streets. A major benefit from these improvements is the connection of Lake Merced, Fort Funston and Ocean Beach in a safe and friendly way for cyclists and pedestrians.With good roundabout design, the appropriate public education and stakeholder support, the newly designed Skyline Boulevard can be an exemplary case of roundabout implementation and, who knows, could even be recognized by the British Roundabout Appreciation Society.