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Red Light Cameras

Effect of Yellow-Interval Timing on Red-Light-Violation Frequency at Urban Intersections

Author: James A. Bonneson, P.E.
Research Engineer
(979) 845-9906
fax: (979) 845-6254

Karl H. Zimmerman
Assistant Research Scientist

Texas Transportation Institute
The Texas A&M University System
3135 TAMU College Station, TX 77843-3135

Submitted for Consideration of Presentation and Publication at:
Transportation Research Board
83rd Annual Meeting
January 2004
Washington, D.C.

July 29, 2003

Statistics indicate that red-light-running has become a significant safety problem throughout the United States. It is estimated that about 200,000 red-light-running-related collisions occur at signalized intersections in the U.S. each year. There is a wide range of potential countermeasures to the red-light-running problem. The objective of this research is to quantify the effectiveness of an increase in yellow interval duration as an engineering countermeasure to red-light violations.

A before-after study is described and the resulting data used to quantify the effect of increasing the yellow interval on the frequency of red-light violations. Based on this research, it was concluded that:

  1. An increase of 0.5 to 1.5 s in yellow duration (such that it does not exceed 5.5 s) will decrease the frequency of red-light-running by at least 50 percent;
  2. Drivers do adapt to the increase in yellow duration; however, this adaptation does not undo the benefit of an increase in yellow duration;
  3. Increasing a yellow interval that is shorter than that obtained from a proposed recommended practice published by the Institute of Transportation Engineers (ITE) is likely to yield the greatest return (in terms of a reduced number of red-light violations) relative to the cost of retiming a yellow interval in the field.

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