Roundabouts are one of the most effective intersection control treatments available with the added benefit of calming traffic. They limit vehicle speeds to approximately 20 mph and can control vehicle speeds on four roads simultaneously. Roundabouts typically reduce crashes by 40 to 60 percent, reduce injury by 35 to 80 percent and almost completely eliminate incapacitating injury and fatal crashes. Community gateways and main roadways are effective locations for roundabouts as they slow traffic and provide space for an aesthetically pleasing entrance treatment.
Roundabouts vs. Traffic Signals
Roundabouts have proven to be much safer than traffic signals. The projected injury crash rate for roundabouts is half that of traditional signals.
Roundabout Crash Reduction
There are two basic premises in which roundabouts achieve crash reductions and greatly reduce severity on those few crashes that do occur. One is the simple decision making and the second is the low level of conflicts. At a four-way intersection, there are 32 possible conflict points between vehicles, whereas there are only eight at roundabouts.
Modern Roundabouts vs. Traffic Circles
There are many differences between roundabouts and traffic circles. Unlike traffic circles, roundabouts are used on higher volume streets to allocate right of way between competing intersection movements. Traffic circles have a large diameter, which contributes to high circulating speeds; roundabouts have a smaller diameter, promoting low circulating speeds. Roundabouts have lower entry speeds compared to traffic circles and feature a yield at every entry point, promoting low speed and no weaving.
Driving Modern Roundabouts
Research shows that drivers quickly adapt to the roundabout traffic flow. For instance, Vail and Avon, Colorado, both feature many high capacity roundabouts and are major tourist destinations with thousands of first-time roundabout drivers using the roundabout intersections each year. Despite large numbers of drivers who have not driven roundabouts previously, these intersections work well and do not confuse motorists. Proper use of signing and road striping at roundabouts assists motorists and minimizes the potential for confusion.