A diverter is an island built at a residential street intersection that prevents certain through and/or turning movements. Diverters affect people living in the neighborhood more than any one else. Therefore, diverters should be considered only when less restrictive measures are not appropriate.

Four types of diverters are: diagonal, star, forced turn, and truncated. A diagonal diverter breaks up cut-through movements and forces right or left turns in certain directions. A star diverter consists of a star-shaped island placed at the intersection, which forces right turns from each approach. A truncated diagonal diverter is a diverter with one end open to allow additional turning movements. Other types of island diverters can be placed on one or more approach legs to prevent through and left-turn movements and force vehicles to turn right.

As with other traffic management tools, diverters must be used in conjunction with other traffic management tools within the neighborhood street network. Any of these diverters can be designed for bicycle and pedestrian access.

• Discourage or prevent traffic from cutting through a neighborhood.
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• Impacts residents more than through traffic.
• Consider less restrictive measures first.
• Evaluate traffic patterns to determine whether other streets would be adversely affected.
• Design diverters to allow bicycle, pedestrian, and emergency vehicle access. If this cannot be done and the street is a major bicycle corridor, a diverter should not be used.
• Diverters generally do not effectively address midblock speeding problems.
• Diagonal diverters may be used in conjunction with other traffic management tools and are most effective when applied to the entire neighborhood street network.
• Diverters should have strong neighborhood support.
• The effect of diverters on service vehicles should be considered.
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  Estimated Cost
$15,000 to $45,000 each, depending on the type of diverter and the need to accommodate drainage.
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  Case Studies
Portland, OR 
Clark County, WA 
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Photo by Dan Burden
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Portland Office of Transportation
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U.S. Department of Transportation Federal Highway Administration