HomeMy WebLinkAbout2020 FAQ-RoundaboutsROUNDABOUTS | FREQUENTLY ASKED QUESTIONS
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EFFECTIVENESS OF ROUNDABOUTS & DESIGN FEATURES
USING ROUNDABOUTS
Why do we use roundabouts?
Aren’t traffic signals safer than roundabouts for pedestrians?
What are the features of a good roundabout design?
Is the roundabout like a 4-way stop?
What are the benefits of roundabouts?
Roundabouts can offer a good solution to safety and capacity problems at intersections.
• In Iowa, intersections that have been replaced with roundabouts have seen a reduction in crashes of all types.
• Roundabouts offer high capacity at intersections without requiring the expense of constructing and
maintaining traffic signals.
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 crossing 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.
• Approach roads should be sufficiently curved, far enough in advance of the roundabout, to reduce
speeds of entering drivers.
• Islands separating the approach and exit lanes, known as splitter islands, should extend far enough from
the roundabout to provide pedestrian refuge and delineate the roundabout.
• Traffic signs, pavement markings, and lighting should be adequate so that drivers are aware that they
are approaching a roundabout and should reduce their speed. With multi-lane roundabouts, signing
and pavement markings should help drivers choose the appropriate lane when entering and exiting the
roundabout.
Aside from the lack of a traffic signal, roundabouts and 4-way stops aren’t similar.
Compared to other intersection types, roundabouts have demonstrated benefits such as:
• Improved Traffic Safety
• Improved Pedestrian Safety
• Reduced Congestion
• Reduced Pollution and Fuel Usage
• Lower Operating and Maintenance Costs
4-Way Stops
• Yield to whomever arrives
first/vehicle on the right
Roundabouts
• Yield to the left, like a right turn on red
• Each driver chooses a safe gap to enter and no
drive “gets a turn”
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Are roundabouts always appropriate?
Should I use my turn signals in a roundabout?
When do I enter a roundabout?
Should I stop inside the roundabout to let someone in?
Can roundabouts accommodate larger vehicles?
Do drivers favor roundabouts?
No. The choice of using a roundabout versus a traffic signal is a case-by-
case decision that must take into account elements such as traffic volumes,
land use, topography and corridor.
Yes, especially when exiting the roundabout. Doing so allows vehicles
waiting to enter the roundabout to know your intentions.
Roundabouts are not like four-way stops in the fact that there is not taking
of turns among vehicle operators. Vehicle operators should enter the
roundabout when there is a safe gap in the traffic flow.
No. Vehicle operators in the roundabout may slow down so that the safe
gap becomes more obvious to the driver wanting to enter the roundabout;
however, they should not stop. Vehicle operators should not stop after
crossing the yield line and are actually in the roundabout circle.
Yes. To accommodate vehicles with large turning radii such as trucks,
buses, and tractor-trailers, roundabout provide an area between the
circulatory roadway and the central island, known as a truck apron, over
which the rear wheels of these vehicles can safely track. The truck generally
is compose of a different colored material than the paved surface, usually
a reddish colored concrete, to discourage routine use by smaller vehicles.
Drivers may be skeptical, or even opposed to roundabouts when they
are proposed. However, opinions quickly change when drivers become
familiar with roundabouts.
A 2002 Institute study in three communities where single-lane roundabouts
replaced stop sign-controlled intersections found 31 percent of drivers
supported the runabouts before construction compared with 63 percent
shortly after.
Another study surveyed drivers in three additional communities where
single-lane roundabouts replaced stop signs or traffic signals. Overall,
36 percent of drivers supported the roundabouts before construction
compared with 50 percent shortly after. Follow-up surveys conducted in
these six communities after roundabouts had been in place for more than
one year found the level of public support increased to about 70 percent
on average.
Typical 4-leg Intersection
4-leg Roundabout
Appropriate Locations
for a Roundabout
Sources of Information
32 vehicle-to-vehicle
conflict points
24 vehicle-to-pedestrian
conflict points
8 vehicle-to-vehicle
conflict points
8 vehicle-to-pedestrian
conflict points
High crash rate locations
Intersections with large
traffic delays
Complex geometry
(more than four approach
roads for example)
Frequent left-turn
movements
www.safety.fhwa.dot.gov
www.iowa.gov
www.dot.wi.gov
www.dot.state.mn.us