Roundabouts

Description
A roundabout is a circular, raised island with deflector islands that form a hub for the traffic that flows around it and the streets that shoot off it. Traffic circulates within roundabouts in a counter-clockwise direction and exits the roundabout by turning right onto the desired street. Unlike a signalized intersection or a mini-traffic circle, drivers select gaps in the traffic to enter the roundabout from each approaching street without having to stop but having to yield to vehicles already engaged in the roundabout.


Issues Addressed

  • Speeding
  • Accidents


Applications

  • Collectors, arterials @ intersections

Advantages 

  • Reduces vehicle speeds.
  • Reduces intersection collisions as compared to signalized intersections and 4-way stops.
  • Opportunity for landscaping and visual enhancements to the neighborhood.
  • May increase intersection capacity depending on turning movements.


Disadvantages

  • May require major reconstruction of an existing intersection
  • Continuous flow of traffic limits opportunity for pedestrians to cross (compared to signal).
  • May reduces response times for emergency vehicles.
  • May require a learning curve when first installed.


Design/Installation Considerations

  • Careful design needed to accommodate bicyclists and pedestrians.
  • May require additional use of right-of-way to accommodate buses and large vehicles.

Proposed roundabout for Springer @ Berry
(not implemented)


Cristo Rey Dr., Cupertino, CA

Alameda, CA