department of public works
Driving A Modern Roundabout
Rules of the Road
- Slow down when approaching a roundabout.
- Yield. All entering vehicles must yield to circulating traffic in the roundabout. Look to the left for circulating traffic and enter when it is safe.
- Choose your lane upon entering the roundabout based on your desired exit or destination:
- The right lane is for straight-through movements or right turns.
- The left lane is for straight-through movements, left turns or U-turns.
- Do not change lanes. Maintain your lane position until exiting the roundabout.
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 streets simultaneously. Roundabouts typically reduce crashes by 40 – 60 percent, reduce injury by 35 – 80 percent and almost completely eliminate incapacitating injury and fatal crashes.
Community gateways and main streets are effective locations for roundabouts as they slow traffic and provide space for an aesthetically pleasing entrance treatment. In addition to the beauty they can provide if landscaped well, roundabouts slow traffic and help pedestrians cross the street.
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. Additionally, Dublin’s proposed roundabouts would be able to accommodate traffic volume growth in the area through 2025 compared with the programmed traffic signal with minimal turn lanes, which would accommodate through 2009.
Roundabout Crash Reduction
There are two basic premises in which roundabouts achieve crash reductions of 40 to 60 percent when compared to traffic signals 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 and only eight at roundabouts. Pedestrians face six conflicts when crossing only one leg of the road whereas at a roundabout they only have two. See figures below:
Difference Between Modern Roundabouts and 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.