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Roundabouts––Frequently 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
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:
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 single–lane
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 one–way 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
case–by–case 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
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 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.
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