Rotary: high speeds on approaches and usually within the circle, not pedestrian friendly.
What is a Modern Roundabout?
There are four points that differentiate a modern roundabout from similar or related traffic control features.
- Entering traffic yields (this is true no matter how many lanes are on the approach).
- Other styles may have circulating traffic yield to entering traffic.
- Approaches are channelized to deflect traffic into the flow.
- Other styles may not use channelization, or deflection may not exist.
- Designed to slow the speed of vehicles through deflection of the vehicle path.
- Other styles may not be designed to slow traffic.
Why a roundabout?
Improve safety; the roundabout has zero vehicle crossing conflict points as opposed to the 16 vehicle crossing conflict points at the 4-leg intersection. Pedestrians are faced with simpler decisions at a time and they travel shorter distance and with two less hazardous conflicts then at conventional intersections (whether stopped or signal controlled).
Save money, less signaling equipment to install, less power, and less maintenance.
Complement community values, roundabouts can operate quieter than conventional signalized intersections because of fewer start-ups and braking by vehicles.
Roundabouts offer the opportunity to provide attractive entries or centerpieces to communities. However, hard objects in the central island directly facing entries are a safety hazard. The central island offers opportunities for aesthetic landscaping and pavement textures can be varied on the aprons.