




	January 2008 Modern Roundabouts Improve Intersection Safety TEA Grants Encourage Business Development Stormwater Planning, Construction Grants Available Current Issue www.AyresAssociates.com Subscribe		Modern Roundabouts Improve Intersection Safety (January 2008)
			You may have noticed more and more modern roundabouts being constructed across Wisconsin and the United States. In fact, to date more than 25 roundabouts are in use on local roadway systems in Wisconsin and more than 30 roundabouts are in use on the Wisconsin state highway system. According to the Wisconsin Department of Transportation (WisDOT), more than 140 intersections are being evaluated for use of roundabout control on the statewide system. What is a modern roundabout? A modern roundabout is a circular intersection in which traffic travels counterclockwise around a central island. Vehicles enter the intersection by yielding to the circulating traffic and exit by proceeding around the central island and making a right-hand turn in the desired direction. Each roundabout is unique to its location because of: Traffic demands. Existing or proposed right-of-way availability. Angle of the intersecting roadways. Some roundabouts have bypass lanes – right-turn lanes that allow a vehicle to make a free-flow right turn instead of having to enter into the intersection. Modern roundabouts are sometimes confused with the older circular intersections, rotaries, or traffic circles. A modern roundabout is much smaller than a rotary or traffic circle, does not allow parking within the circular intersection, and has three defining features that set it apart from these older circular intersection designs: Yield control at entry. Approaches channelized or defined by islands. Entering vehicle speeds reduced by deflection of the entry approach. Why use roundabout control? This new form of intersection control provides safe and efficient traffic flow by slowing vehicle speeds through the intersection and reducing the number of collision points in the intersection (when compared with a typical four-legged intersection) as shown on the next page. A study comparing collisions of traditional traffic-signal-controlled intersections completed for the Insurance Institute for Highway Safety indicates roundabouts provide a: 90% reduction in fatal crashes. 76% reduction in injury crashes. 30% to 40% reduction in pedestrian crashes. 10% reduction in bicycle crashes. Roundabout control also reduces travel delays during non-peak travel times. Have you ever had to wait for the green light at a traffic-signal-controlled intersection when there were no other vehicles traveling near the intersection? Roundabout control eliminates this waiting period. How do drivers learn to use roundabouts? When a new modern roundabout is designed for an intersection, communities, engineering consultants, and WisDOT staff help to educate drivers, pedestrians, and bicyclists in roundabout use. Public information meetings frequently provide an educational forum, and many communities have developed handouts with roundabout driving tips. In general, drivers need to: Slow down and watch for traffic signs. Yield to pedestrians and bicyclists when entering and exiting a roundabout. Keep your speed low in the roundabout. 10% reduction in bicycle crashes. Turn right onto your destination street. A new roundabout in the neighborhood may take a little getting used to, but the end result is an intersection that keeps traffic moving safely and efficiently. Intersections come with "collision points" - areas where vehicles merge, diverge, and cross and where crashes can happen. An intersection with four single-lane approaches (shown at left) has up to 32 collision points. A modern roundabout (shown at right) has only eight collision points.