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MYTHS
 
FACTS
Roundabouts and traffic circles are the same thing.

Take a look at the following comparison of the Kingston, New York Roundabout. [ Move mouse over photos below to see the change ]




By using bypass lanes (shown above) this roundabout allows many drivers to travel through the area without entering any intersection at all, and provides better safety and performance for drivers making left turns.

The Seattle Times reported in June 2002 that at least 600 roundabouts have been built in the United States since 1990. For more information visit the links page.


       In their travels, many Anchorage residents have experienced old-style traffic circles. Some Anchorage residents have experienced modern roundabouts, and some residents have experienced both. Traffic circles are common in many places in the U.S. including Washington DC, New Jersey, and Pennsylvania. Modern roundabouts are relatively new to the U.S., but they are common in the United Kingdom and Australia and are becoming very popular in many other European countries.

       Based on their travel experiences, Anchorage residents are likely to agree that nonconforming traffic circles don't work very well. For those travelers who have only encountered old-style traffic circles, it is important to understand why modern roundabouts move traffic safely and efficiently before they are used in Anchorage.
       There are three principals that explain the superiority of modern roundabouts: yield rules, deflection, and flare.


Typical Modern Roundabout
This is NOT a Roundabout
 


Dupont Traffic Circle in Washington D.C.

MODERN ROUNDABOUT
PRINCIPLES
NONCONFORMING TRAFFIC CIRCLE

Yield-at-Entry Rule:

  • Entering traffic yields to circulating traffic, which always keeps moving.
  • Very efficient with heavy traffic.
  • No weaving distance is needed, so roundabouts are small and fit in compact spaces.

Entering traffic may interfere with circulating traffic:

  • Circulating traffic can not clear when entering traffic fills circle.
  • Heavy traffic causes gridlock.
  • Circles must be large to provide long weaving distances.

Entering traffic is deflected slowly around the central island:

  • Deflection controls speed without enforcement, thereby reducing accidents.
  • Deflection forms gaps in traffic so other vehicles can enter.
  • Entry flare adds lanes

Inconsistent entry design may allow traffic to enter at high speed:

  • Serious accidents can result on high speed streets.
  • Fast entries impede gap acceptance and defeat the yielding process.

Flare increases capacity at the intersection, where capacity is needed most:

  • Flare promotes narrow streets between roundabouts, saving cost and neighborhood impacts.

Poor entry conditions may not benefit from flare:

  • Poor intersection capacity even with large traffic circles.
  • Higher capacity requires wide streets between circles, wasting money and land

Other Myths and Facts

Roundabouts cause more crashes than the stop signs or signals they replace.
Roundabouts cause longer commutes.
The public will never accept roundabouts.
Roundabouts are difficult to maneuver.
Roundabouts cost more.
Roundabouts are not good for pedestrians and bicyclists.

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