United States Department of Transportation
i
Characterize dynamic dilemma zone and minimize its effect at signalized intersections : December 26, 2008.
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2008-12-26
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By Wei, Heng
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Abstract:Dilemma zone at signalized intersection has been recognized as a major potential causing rearend
crashes, and has been widely studied by researches since it was initially proposed as the
GHM model in 1960. However, concepts conventionally defined to represent yellow phase
dilemma lack integrity. This research conducts a comprehensive literature review with attempt to
clarify the interrelationship among dilemma zone, option zone, and indecision (decision) zone,
and to develop a heuristic framework to present the contributing factors in dilemma zone
modeling. A new method for modelling the locations and lengths of the dilemma zone using
video-capture techniques and vehicle trajectory data is presented in this report. First, dilemma
zone is mathematically modeled based on the literature review. Then, field-observed trajectory
data extracted by the video-capturing-based approach are used to calibrate the contributing
factors involved in the dilemma zone models. The high accuracy of the time-based trajectory
data has significantly enhanced the accuracy of the calibrated dilemma zone models. Two sets of
trajectories are explored for calibrating the dilemma zone contributing factors. One is concerned
with maximum yellow-onset safe passing distance and minimum yellow-onset stopping distance.
The other is concerned with Xth percentile yellow-onset passing distance and stopping distance
for the prevailing travel behaviors. The latter alternative actually precludes “too conservative”
and “too aggressive” behaviors in response to yellow indications.
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