Abstract
The method of limits was used in a driving simulator study to determine the time-to-stop line (TSL) on the approach to a signalized intersection at which drivers were equally likely to stop or proceed in response to the onset of a yellow change interval. Data from 191 drivers are presented. The mean TSL is referred to as the driver decision point. The variability in the decision point of individual drivers is also reported. The decision point data are discussed in terms of the dilemma zone. It was concluded that the 1-s reaction time that was typically used for calculation of the appropriate yellow and all-red intervals was appropriate. A wide variation in the decision point between drivers was found (1.65 to 5.3 s), and the 10th and 90th percentile decision points were 2.10 s and 3.75 s, respectively. The presence of other vehicles did not appear to affect the decision point. The method of limits is recommended as a quick and reliable means of measuring a driver's decision point with respect to the onset of the yellow change interval. The method may be useful in research settings for assessing treatments intended to influence driver reactions to the yellow change interval.
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