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RoundaboutsFrequently Asked Questions
Roundabouts, rotaries, traffic circles they're all the same, aren't they?
Why do roundabouts need to be so big?
Why is Maryland installing roundabouts?
Aren't traffic signals safer than roundabouts for pedestrians?
Are roundabouts safe near schools?
Are roundabouts appropriate everywhere?
I drive a big truck, and that roundabout looks awfully tight. Will I fit?
I'm driving in a multilane roundabout. How do I choose which lane to enter and exit?
What should I do when I'm in a roundabout when an emergency vehicle arrives?
How about riding a bicycle through a roundabout?
Should the circulatory roadway of a multilane roundabout be striped?
What about snow removal at roundabouts?
Q1: Roundabouts, rotaries, traffic circles they're all the same, aren't they?
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 rightofway 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 generally a higher degree of safety. [back]
Q2: Why do roundabouts need to be so big?
A2: The size of a roundabout is determined by capacity needs, the size of the largest vehicle, 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 singlelane roundabout needs to be at least 100 feet in diameter and is typically 120 to 140 feet in diameter. [back]
Q3: Why is Maryland installing roundabouts?
A3: Roundabouts can offer a good solution to safety and capacity problems at intersections. At intersections where roundabouts have been installed in Maryland to replace existing intersections, accidents of all types have been reduced by over 60 percent, and injury accidents have been reduced by over 75 percent. Roundabouts can also offer high capacity at intersections without requiring the expense of constructing and maintaining a traffic signal. [back]
Q4: Aren't traffic signals safer than roundabouts for pedestrians?
A4: It depends on the amount of pedestrians and vehicles. In many cases a roundabout can offer a safer environment for pedestrians than a traffic signal because the pedestrian crossing at a roundabout is reduced to two simple crossings of oneway traffic moving at slow speeds. A pedestrian crossing at a traffic signal still needs to contend with vehicles turning right or left on green, vehicles turning right on red, and vehicles running the red light. The latter of these potential conflicts occur at high speeds and often result in injuries or fatalities to pedestrians. [back]
Q5: Are roundabouts safe near schools?
A5: Several roundabouts have been installed near schools in the United States, including locations in Montpelier, Vermont; Howard, Wisconsin; University Place, Washington; and Kennewick, Washington. None has reported any significant problems. For the Howard, Wisconsin, location, prior to the opening of the roundabout, the school required all school children to arrive by bicycle or car because it was unsafe to cross the street. Since the roundabout opened, children now have a safe crossing location, aided by a crossing guard. [back]
Q6: Are roundabouts appropriate everywhere?
A6: No. The choice of using a roundabout versus a traffic signal is a casebycase decision. The Maryland State Highway Administration evaluates each candidate intersection individually to determine whether a roundabout or a traffic signal is more effective. [back]
Q7: I drive a big truck, and that roundabout looks awfully tight. Will I fit?
A7: Yes. The roundabout has been designed specifically 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 the roundabout, 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. Click here for a demonstration of this.
At a multilane roundabout, you may need to occupy the entire circulatory roadway to make the turn. Signal your intention in advance and claim both lanes on approach to the roundabout. [back]
Q8: I'm driving in a multilane roundabout. How do I choose which lane to enter and exit?
A8: In general, approach a multilane roundabout the same way you would approach any other intersection. If you want to turn left, use the leftmost lane and signal that you intend to turn left. If you want to turn right, use the rightmost 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 as you pass the exit before the one you want to use. [back]
Q9: What should I do when I'm in a roundabout when an emergency vehicle arrives?
A9: If the roadway in the roundabout is wide enough, you may be able to pull as far to the right as possible and allow the emergency vehicle to pass. However, it is generally better to completely clear the intersection and pull off to the side past the roundabout. [back]
Q10: How about riding a bicycle through a roundabout?
A10: A bicyclist has a number of options at a roundabout, and your choice will depend on your degree of comfort riding in traffic. The speed of cars through a roundabout are typically 15 to 25 mph, close to the speed you ride your bicycle. You can choose to either circulate as a vehicle or use the sidewalk around the roundabout. When circulating as a vehicle, be sure to ride near the middle of the lane so that drivers can see you and will not attempt to pass you. Remember that cars should be traveling at speeds similar to your speeds. [back]
Q11: Should the circulatory roadway of a multilane roundabout be striped?
A11: There is no international consensus on this question. In the United Kingdom, the general practice is to not stripe, although they will stripe some complicated multilane roundabouts where it improves operations. In Australia, the general practice is to stripe the circulatory roadway. In Maryland, we have done some limited striping of our multilane roundabouts, primarily to aid exiting vehicles. [back]
Q12: What about snow removal at roundabouts?
A12: A number of communities in snowy areas have installed roundabouts, including Howard (Green Bay), Wisconsin; Montpelier, Vermont; and Vail, Colorado. All have indicated that while there is some initial adjustment in procedures for snowplow crews, roundabouts generally 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. [back]
All content contained within these materials is the intellectual property of Maryland State Highway Administration.
© 2000 Maryland State Highway Administration.
Last modified: Tuesday July 9, 2000.