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Roundabouts: Questions and Answers


Questions...

Roundabouts, rotaries, traffic circles – they're all the same, aren't they?

Are roundabouts better than traffic signals for pedestrians?

Are roundabouts appropriate everywhere?

Can roundabouts accommodate large vehicles such as fire engines, school buses and horse trailers?

What should I do when I'm in a roundabout when an emergency vehicle arrives?

How about riding a bicycle through a roundabout?

How is the size of a roundabout determined?


Answers...

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 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 generally a higher degree of safety. [back]

 

Q2:  Are roundabouts better than traffic signals for pedestrians?

A2: A roundabout can offer an improved environment for pedestrians compared to a traffic signal.  Depending on the number of pedestrians and vehicles that use the intersection.  A pedestrian crossing at a roundabout makes two simple crossings of one-way traffic moving at slow speeds.  A pedestrian crossing at a traffic signal must contend with vehicles turning right or left on a green light and vehicles turning right on a red light.  Vehicles running red lights, usually speeding directly through an intersection, are a danger to pedestrians.  Roundabouts will not allow speeding vehicles to proceed straight through an intersection. [back]

 

Q3:  Are roundabouts appropriate everywhere?

A3:  No.  Each intersection must be evaluated individually to determine whether a roundabout, stop signs or a traffic signal is more effective.   The volume and speed of traffic, the number of pedestrians using the intersection, and additional factors must be considered. [back]

 

Q4:  Can roundabouts accommodate large vehicles such as fire engines, school buses and horse trailers?

A4:  Roundabouts are designed specifically to accommodate large vehicles including fire trucks, school buses and trucks with horse trailers.  As drivers approach the roundabout, they should stay close to the left side of the entry.   As they pass through the roundabout, the vehicle trailer may pass over the special apron around the central island - the apron is designed specifically for this purpose. [back]

 

Q5:  What should I do when I'm in a roundabout when an emergency vehicle arrives?

A5:  If the roadway in the roundabout is wide enough, safely pull to the right and allow the emergency vehicle to pass.  However, if there is time, it is generally better to drive out of the roundabout and pull over on the right side of the street. [back]

 

Q6:  How about riding a bicycle through a roundabout??

A6:  A cyclist has a number of options at a roundabout, and the choice will depend on the cyclist’s degree of comfort riding in traffic.  The speed of cars through a roundabout is typically 15 to 25 mph, similar to the average speed of an adult bicycle rider.  Experienced cyclists choosing to enter the roundabout should stay in the roadway and follow the flow of traffic; other options include walking the bicycle on adjacent sidewalks or riding on multi-use paths.  Cyclists using the roadway should ride near the middle of the lane so that drivers can see them and not attempt to pass them. [back]

 

Q7:  How is the size of a roundabout determined?

A7:  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 45 feet or more, a single–lane roundabout needs to be at least 120 feet in diameter and is typically 110 to 130 feet in diameter. [back]


Questions about roundabouts?
Contact Traffic Engineering at (480) 312-7696
or email roundabouts@scottsdaleaz.gov