American Society of Civil Engineers

Consistency of Video Detection Activation and Deactivation Times between Day and Night Periods

by Avery Rhodes, P.E., (ITS Mgr., City of Glendale, Glendale, AZ. E-mail:, Kristofer Jennings, Ph.D., (Professor, Statistics, Purdue Univ., School of Civ. Engrg., 550 Stadium Mall Dr., West Lafayette, IN 47907. E-mail:, and Darcy M. Bullock, Ph.D., P.E., (corresponding author), M.ASCE, (Prof., Dept. of Civ. Engrg., Prudue Univ., School of Civ. Engrg., 550 Stadium Mall Dr., West Lafayette, IN 47907-2051 E-mail:

Journal of Transportation Engineering, Vol. 133, No. 9, September 2007, pp. 505-512, (doi:

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Document type: Journal Paper
Abstract: Video detection has become an increasingly popular technology for vehicle detection at signalized intersections. Among the potential disadvantages of this technology is the tendency of video detectors to activate early at night due to headlight reflection on the pavement. This early activation results in a dramatic increase in the length of the effective vehicle detection zone. This observed variation in the effective length of the vehicle detection zone that varies by ambient lighting condition and camera placement presents a very serious impediment for traffic engineers to design vehicle extension intervals that operate consistently during day, night, and transition periods. Further, the stochastic variation in the length of the vehicle detection zone length has the potential to create driver expectancy issues. Tables are included that report the observed average and range of detection zone length variations for 16 observed video cameras that were extensively calibrated by the manufacturer at the test site. The paper concludes by recommending near-side placement of video detection devices to reduce the stochastic variation in detection zone length.

ASCE Subject Headings:
Traffic management
Traffic signals
Traffic surveillance
Traffic control devices
Intelligent transportation systems
Night time