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Development of a framework for evaluating yellow timing at signalized intersections.
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2011-02-01
[PDF-2.37 MB]
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Edition:Final contract.
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Abstract:Studies show that the proper design of clearance intervals has significant implications for intersection safety. For
example, in 2001, approximately 218,000 red-light-running crashes occurred at signalized intersections in the United States.
These crashes resulted in nearly 181,000 injuries and 880 fatalities and an economic loss of $14 billion. Driver behavior while
the driver is approaching high-speed signalized intersections at the onset of a yellow indication varies as a function of many
parameters. Some of these parameters are related to the driver’s attributes, e.g., age, gender, perception-reaction time, and
acceptable deceleration levels. Other parameters that relate to the intersection geometry include the approach speed, distance, and
time to the intersection at the onset of the yellow indication.
This study developed a novice approach for computing the clearance interval duration that explicitly accounts for the
reliability of the design (probability that drivers are not caught in a dilemma zone). Lookup tables based on the limited data
available from this study are provided to illustrate how the framework could be used in the design of yellow timings. The
approach was developed using data gathered along Virginia’s Smart Road test facility for dry and clear weather conditions for
two approach speeds: 72.4 km/h (45 mph) and 88.5 km/h (55 mph). Each dataset includes a complete tracking of the vehicle
every deci-second within 150 m (500 ft) before and after the intersection. A total of 3,454 stop-run records were gathered. These
include 1,727 records (687 running records and 1,040 stopping records) for an approach speed of 45 mph and 1,727 records (625
running records and 1,102 stopping records) for an approach speed of 55 mph. Using these data, models that characterize driver
perception-reaction times and deceleration levels were developed.
The application of the proposed approach demonstrates that the current design procedures are consistent with a
reliability level of 98%.
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