Roundabout Questions and Answers
What is a roundabout?
A roundabout is a generally circular-shaped intersection. Traffic travels through roundabouts in a counterclockwise direction around a center island, with vehicles entering the roundabout yielding to those traveling in the roundabout. Roundabout design often requires vehicles to travel through the intersection at slower speeds, calming traffic and increasing safety. The lower speeds within roundabouts also allow entering traffic to access smaller gaps between circulating vehicles, increasing traffic volume and decreasing delays and congestion.
Are roundabouts different from older traffic circles and rotaries often seen in Europe and the eastern United States?
Modern roundabouts are not the same as traffic circle or rotaries. Modern roundabouts are smaller than older traffic circles and rotaries. Vehicles negotiate a sharper curve when entering modern roundabouts, making travel speeds in roundabouts slower than speeds in traffic circles and rotaries. In some older rotaries and traffic circles, a driver must merge with or weave among high-speed entering or circulating traffic. Modern roundabouts eliminate much of this dangerous weaving found in older traffic circles and rotaries. Additionally, some older traffic circles and rotaries operated according to the traditional "yield-to-the-right" rule, with circulating traffic yielding to entering traffic. In contrast, modern roundabouts require entering vehicles to yield to traffic on the left, as many drivers in this country are accustomed to.
Aren’t roundabouts a new transportation concept?
Much of the world has been utilizing modern roundabouts for decades. In the 1960s, Great Britain experimented with roundabout design to optimize their safety and traffic flow. That experience, as well as experience from Australia, Canada and mainland Europe, has guided the effective design of roundabouts in the U.S. Thousands of roundabouts can now be found throughout the United States, joining the over 30,000 roundabouts in France and the United Kingdom.
Will roundabouts work and be accepted in my area if drivers are unfamiliar with how to drive them?
Roundabouts do not require new driving skills. Entering a roundabout uses many of the same skills as making a right-hand turn out of a driveway. First, yield to pedestrians/bicyclists, then check for traffic approaching from the left. Wait for a suitable gap in traffic and then proceed into the roadway (in this case, the roundabout). Because roundabouts are not familiar to all members of the public, the majority of people often oppose roundabouts in areas where they have not been previously used. After becoming familiar with and using roundabouts, the majority of the public changes opinion to support them. A study published in the Institute of Transportation Engineers Journal examined public perception in areas of Nevada, Kansas and Maryland where roundabouts were being installed. Before construction, over 50 percent of those surveyed were opposed to the project, while only 31 percent were in favor. After construction of the roundabouts, public perception greatly increased, with 63 percent favoring the roundabouts.
Can larger vehicles travel through roundabouts?
Many highway/freeway roundabouts consider the mix of traffic using the road, and can accommodate vehicles with large turning radii such as trucks, buses, and tractor-trailers. Many of these roundabouts provide an area between the roadway and the central island over which the rear wheels of these vehicles can safely go. The area is known as a truck apron. Truck aprons are generally composed of a different material than the paved roadway to discourage routine use by smaller vehicles. Some roundabouts in residential areas that are not often traveled by larger vehicles may not be large enough to accommodate trucks, buses and/or tractor-trailers.
Do roundabouts work in every location?
Roundabouts are appropriate at many intersections, including high-crash locations and locations with large traffic delays, complex road alignments, frequent left-turn turns and relatively-balanced traffic flows. Roundabouts can be constructed along congested arterial roads as well. On the other hand, roundabouts may not be the best option in areas where there is not enough roadway space or where there is a large number of pedestrians. The Nevada Department of Transportation carefully evaluates potential roundabouts on a case-by-case basis to provide the most effective traffic control for each intersection.
What can be done to prevent crashes that may occur at roundabouts?
Despite the safety benefits of roundabouts, some crashes do still occur. An Insurance Institute for Highway Safety study looked at 38 Maryland roundabouts, and found that four types of crashes (run-off-the-road, rear-end, sideswipe and entering vs. circulating) were the most prevalent. The study found no right-angle or head-on collisions, the potentially most severe type of crash that is seen at traditional intersections. Researchers in the study concluded that unsafe, high speeds were a major factor in most of the crashes. Roundabouts are designed with measures that will alert drivers so they can slow in advance. Speed limit signs, roundabout ahead and yield signs, pavement markings and raised landscaping elements in the center of many roundabouts help make drivers aware of an upcoming roundabout and how to safely navigate the roundabout. Motorists are reminded to slow and use caution while entering and driving in roundabouts.
Are roundabouts appropriate for intersections near schools?
Because roundabouts slow vehicle speeds and have safety advantages for both motorists and pedestrians, they are often a good choice near schools. Throughout the nation, many roundabouts have been built near schools, including a Nevada state roundabout installed on State Route 88 in front of Douglas High School.
What do the painted white triangles at the entrance of many roundabouts mean?
The white triangles indicate where vehicles should stop and yield to oncoming traffic already in the roundabout. These triangles are the universal pavement symbol for “yield” and are often used at other intersections and crosswalks as well.