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Traffic Calming Devices →
Horizontal Speed Control Devices |
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| Roundabouts |
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What are Roundabouts?
- Different from traffic circles; usually located on higher volume
roadways and often replace stop signs or traffic signals. They are larger
than traffic circles and can contain raised splitter islands on the
approach to direct traffic counter-clockwise.
- Raised islands usually placed in the center of intersections.
- Typically circular in shape and landscaped.
- Designed so approaching traffic must yield to traffic within the
circle (yield-at-entry). A YIELD sign usually controls traffic on all
approaches.
- Effective by impeding the straight-through movement of an intersection
causing drivers to slow their vehicles as they proceed counter-clockwise
around.
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How are Roundabouts
designed?
- The design varies by neighbourhood and design purpose.
- The circles can be designed to be partially mountable by larger
vehicles. This means that larger vehicles can ride over part of the circle
while making a tight turn or negotiating the intersection.
- It is suggested that on-street parking be prohibited
10 meters from the intersection.
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Where are Roundabouts placed and how much are they?
- Roundabouts are most effective at reducing vehicle speeds when several
are used in series.
- Ideal for residential applications, commercial areas, and business
districts.
- Installation costs of roundabouts vary substantially depending on the
size, approach islands, landscaping, and land acquisition. The costs are
well above those of a traffic circle.
- Landscaping a roundabout adds to the ongoing maintenance costs.
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Advantages
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Disadvantages
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- Effective in reducing vehicle speed.
- Can significantly reduce serious motor vehicle collisions by
reducing right-angle conflicts.
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- May make left turn maneuvers difficult for emergency vehicles
and larger trucks.
- The potential exists for an increase in vehicle/bicycle
accidents and vehicle/pedestrian accidents as vehicles may not yield
properly or be deflected by the circle into a bicycle's or
pedestrian's path.
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Roundabout Issues & Comments
- Proper signage and possibly lighting are necessary to ensure that
drivers understand how to properly negotiate a roundabout.
- The center island doesn't necessarily need to be a circle; it can be
designed to fit the intersection configuration.
- When designing a roundabout, considerable attention should be given to
aesthetics.
- Modern roundabouts are different from older large traffic circles and
rotaries. Modern roundabouts require yield-at-entry and are much smaller.
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