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Chicanes
| Mini-Circles
Lateral
/ Horizontal Shifts
Mini-Circles
Mini-circles are raised circular islands constructed in the center
of residential street intersections. They reduce vehicle speeds by
forcing motorists to maneuver around them and are sometimes used instead
of stop signs. Mini–circles have been found to reduce motor vehicle
crashes by an average of 90 percent in Seattle, WA.11 Drivers making
left turns are directed to go on the far side of the circle (see diagram
at right) prior to making the turn. Signs may be installed within
the circle to direct motorists to proceed around the right side of
the circle before passing through or making a left turn. Mini-circles
are commonly landscaped (bushes, flowers, or grass), most often at
locations where the neighborhood has agreed to maintain the plants.
In locations where landscaping is not feasible, traffic circles can
be enhanced through pavement materials.
Mini-circles are an intersection improvement as well as a traffic
calming device and can take the place of a signal or four-way stop
(many unwarranted signals are installed because of the demand for
action by the community).
Mini-circles must be properly designed to benefit pedestrians and
cyclists. Right-turning vehicles are not controlled at an intersection
with a mini-circle, potentially putting pedestrians and cyclists at
risk. Curb radii should not be reduced to what would be otherwise
desirable. Traffic circles with splitter islands make crossing easier
for pedestrians (especially for persons with disabilities) and control
vehicle movements entering the intersection, but require more space.
The occasional larger vehicle going through an intersection with a
traffic circle (e.g., a fire truck or moving van) can be accommodated
by created a mountable curb in the outer portion of the circle.
A traffic mini-circle helps reduce vehicle
speeds, but still allows cars, buses and other large vehicles to
pass through the intersection with little difficulty.
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The material provided on this page is from the FHWA publication
"Pedestrian Facilities User Guide." This guide is currently under review
by practicioners and others in the field. Subsequently, the material
provided on this page is subject to change in the future.
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Purpose:
• Manage traffic at intersections where volumes do not warrant
a signal.
• Reduce crash problems at the intersection of two local streets.
• Reduce vehicle speeds at the intersection.
• Treat a series of intersections along a local street as part
of a neighborhood traffic improvement program.
Considerations:
• Do not make generous allowances for motor vehicles by increasing
the turning radii —this compromises pedestrian and cyclist safety.
• Larger vehicles that need access to streets (e.g. school buses
and fire engines) may need to make left hand turns in front of the
circle.
• Use yield, not stop controls.
Estimated Cost:
The cost is approximately $6,000 for a landscaped traffic mini-circle
on an asphalt street and about $8,000-$15,000 for a landscaped mini-circle
on a concrete street.
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