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A1: No. Other than sharing a circular shape, a modern roundabout operates much differently than other traffic circles, including rotaries. A modern roundabout requires entering traffic to yield the right–of–way to traffic already in the roundabout. This keeps the traffic in the roundabout constantly moving and prevents much of the gridlock that plagues rotaries, for example. Modern roundabouts are also much smaller than rotaries and thus operate at safer, slower speeds. The design of a modern roundabout allows capacities comparable to signals but with a higher degree of safety.
A2: The size of a roundabout is determined by capacity needs, the size of the largest expected vehicles, the need to achieve appropriate speeds throughout the roundabout, and other factors. To handle typical trucks with overall wheelbases of 50 feet or more, a single–lane roundabout needs to be at least 100 feet in diameter and is typically 120 to 140 feet in diameter.
A3: Roundabouts offer a good solution to safety and capacity problems at intersections. At Maryland intersections where roundabouts were installed to replace existing intersections, accidents of all types have been reduced by over 60 percent, and accidents resulting in injuries have been reduced by over 75 percent. Roundabouts also offer high capacity at intersections without requiring the expense of constructing and maintaining a traffic signal.
A4: It depends on the number of pedestrians and vehicles. In many cases a roundabout offers a safer environment for pedestrians than a traffic signal because the pedestrian crossing at a roundabout is reduced to a pair of one-way traffic moving at slow speed. A pedestrian crossing at a traffic signal contends with vehicles turning both way on green, vehicles turning right on red, and vehicles running the red light. Cars running a red light often drive at high speed and are more likely to injure or even kill pedestrians.
A5: Roundabouts have been installed near schools around the United States, such as in Montpelier, Vermont; Howard, Wisconsin; and Kennewick, Washington. None has reported any significant problems. For Howard, Wisconsin, before opening the roundabout, the school required all school children to arrive by bicycle or car because it was unsafe to cross the street. Now Howard's children, aided by a crossing guard, have a safe crossing location.
A6: Erecting a roundabout versus a traffic signal is a case-by-case decision. The Maryland Department of Transportation State Highway Administration (MDOT SHA) evaluates each candidate intersection individually to determine whether a roundabout or a traffic signal will be more effective.
A7: Yes. Roundabouts are designed to accommodate large vehicles such as yours. As you approach the roundabout, stay close to the left side of the entry. As you pass through, your trailer may drag over the special apron around the central island – it was designed specifically for this purpose. As you exit, again stay close to the left side of the exit.
At a multilane roundabout, you may need to occupy the entire circulatory roadway to make the turn. Signal in advance and claim both lanes on approach to the roundabout.
A8: Approach a multilane roundabout the same way you would approach any other intersection. If you want to turn left, use the left-most lane and signal that you intend to turn left. If you want to turn right, use the right-most lane and signal that you intend to turn right. In all cases, pass counterclockwise around the central island. When preparing to exit, turn on your right turn signal at the exit just before your exit.
A9: If the roundabout roadway is wide enough, pull as far to the right as possible and allow the emergency vehicle to pass. It is better to completely clear the intersection and pull off outside the roundabout.
A10: A bicyclist has a number of options, and your choice depends on your degree of comfort riding in traffic. Cars in roundabouts typically drive 15 to 25 mph, close to the speed you ride your bicycle. You can circulate with cars or use the sidewalk around the roundabout. When circulating as a vehicle, ride near the middle of the lane so that drivers see you and do not pass you.
A11: A number of communities in snowy areas have roundabouts, including Howard (Green Bay), Wisconsin; Montpelier, Vermont; and Vail, Colorado. All report that roundabouts present no major problems for snow removal. In Howard, Wisconsin, for example, one truck will start on the truck apron and plow around the roundabout to the outside, while another truck will plow each entry and exit, pushing the snow to the outside. Roundabouts make it easier to turn snowplows as well.
All content contained within these materials is the intellectual property of the Maryland State Highway Administration.
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