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TRAFFIC CIRCLE CHAPTER 22 <br />A traffic circle is a raised geometric control <br />island, frequently circular, in the center of an <br />intersection of local streets. A typical traffic <br />circle would be about 20 feet in diameter. <br />Traffic traveling through the intersection must <br />avoid the island. This affects the path and <br />speed of the traffic. Traffic circles can be used <br />with or without stop sign control of the inter- <br />section. The approach roadway widths <br />should be 30 feet wide or wider. Frequently, <br />the island is landscaped with low growing <br />shrubs and a tree. <br />Effects <br />Volumes. The impact on the traffic volume is <br />minimal. Some vehicles may be diverted to <br />adjacent collector or arterial streets to avoid <br />the islands. <br />Speed. Speeds near the intersection are <br />reduced so that the vehicles can avoid the <br />traffic circle. This is especially true of left <br />turning vehicles. Speed in the middle of the <br />block may increase as some drivers try to <br />make up for lost time. <br />Traffic Noise, Air Quality and Energy Con- <br />sumption. There is an increase in noise and <br />energy consumption from the deceleration <br />and acceleration of vehicles. Air quality is <br />negatively affected as well. <br />Traffic Safety. Depending on the accident <br />patterns, a positive change in accidents could <br />occur. If there are a number of right angle <br />accidents, a significant reduction will possibly <br />occur. This is the result of a slowing of traffic <br />at the point of conflict. If there are few right <br />Neighborhood Traffic Control January 1994 <br />angle accident or there is stop control at the <br />intersection already, there will probably be <br />little effect on accidents. <br />Community Reaction. The reaction is mixed. <br />Some drivers express concern about an un- <br />necessary obstruction and potential hazard. <br />There are a few complaints regarding noise, <br />air quality, or energy consumption. Depend- <br />ing on the kind of construction and landscap- <br />ing, the traffic circle can receive varying <br />opinions on their aesthetic value. Loss of <br />parking in areas of heavy parking can cause <br />complaints. The ability to maneuver around <br />the traffic circle before the streets are cleared <br />of snow can also cause complaints. <br />Cost <br />The cost of a typical traffic circle with concrete <br />curb and gutter and landscaping can ap- <br />proach $5,000. <br />Page 22 <br />