The Isolated Signalized Intersection as a Mitigation on a High-Speed Highway

by Thomas C. Ferrara, CSU-Chico, Chico, United States,
A. Reed Gibby, CSU-Chico, Chico, United States,
Simon P. Washington, CSU-Chico, Chico, United States,

Document Type: Proceeding Paper

Part of: Site Impact Traffic Assessment: Problems and Solutions


A concentrated 'leap-frog' type development is commonly proposed as it offers the opportunity to organize an extensive living-recreation orientated site with low to modest land costs. A concentration of new traffic will often warrant a signal at an isolated intersection. Of concern is safety at such signalized intersection which serve traffic with high approach speeds. A study of accident experience at 40 isolated signalized intersections in California indicated actions which appeared to be effective in warning approaching motorists of a possible stop include an advanced warning sign with a flashing beacon and the addition of backplates to the signal heads to provide contrast. A separate left turn lane, left turn phase, and a raised median on a high speed approach also correlate with lower accident rates. These features are common in urban and suburban areas and thus approaching motorists are more likely to expect a signal. Approaches with wide paved shoulders, maximum detector setback, and extended intergreen times also proved to have fewer accidents.

Subject Headings: Traffic signals | Intersections | Traffic signs | Left turns | Highway engineering | Traffic surveys | Traffic models | Traffic safety | California | United States

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