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Modified T-Intersections:

This design treatment is intended for certain T-intersections on lower-volume streets in residential areas where there is a need to reduce the speeds of through traffic. It involves a gradual curb extension or bulb at the top of the T, such that vehicles are deflected slightly as they pass straight through the intersection (see diagram). This type of design can help to discourage cut-through traffic in a neighborhood and can reduce speeds at the intersection. If not properly designed, it can create confusion regarding priority of movement. Consider a mini-circle before installing this treatment.

Photo by Dan Burden
This modified T-intersection in Portland, Oregon, is intended to reduce speeds of through traffic as well as restrict left-turning vehicles.

• Reduce vehicle speeds through a T-intersection on a low-volume street.
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• Used when vehicle volumes are low to moderate.
• A mini-traffic circle may accomplish the same objective and may be less costly and confusing.
• If designed to eliminate some turning movements, the affected neighborhood residents should be consulted for input and an analysis of traffic patterns done to ensure that through traffic would not be diverted inappropriately.
• Pedestrian and bicycle access must be accommodated through the island.
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  Estimated Cost
$20,000 to $60,000, depending on the design and whether drainage and utilities need to be relocated.
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