Title The Design of Traffic Control Signal Change Interval: Theories and Practices
Dept Transportation Engineering, Maritime and Air Transport Division
Year 2013
Month
Price
Summary The main purpose for setting traffic control signal change intervals is to warn drivers that their right of way will soon be ended, as well as to offer buffer time for moving vehicles to stop safely or pass through the intersection completely during change in signal indications, in order to avoid unnecessary accidents.

　　In regard to the design of signal change intervals, Matson proposed a simple formula as early as in 1929. Gazis et al. proposed a complete formula in 1960, which was later adopted by the Institute of Transportation Engineers (ITE). But Gazis’ formulas was continually being questioned by engineering professionals, since the required amber-light duration would become longer as the approach speed became higher after the parameters in the formula had been set. The formula was observed to be unrealistic when put into practice. Surprisingly, there is currently still no consensus on the design of signal change intervals, nor has there been an official standard proposed by ITE. Shortly, design of change intervals has been in controversy for over 80 years and still lacks complete theory.

　　The purpose of this study is to construct a new and comprehensive theory to make up for the current deficiencies in design of change intervals. In addition to correcting past errors and clarify the aggregated stopping possibility function proposed earlier, a performance indictor “vehicles which entered the intersections after an amber light (α(β))” for design of amber/all-red light duration was proposed. This research aimed to find a clear theory as well as a simple applicable formula for the design of signal change intervals. It discovered that the maximum of vehicles entering the intersections after an amber light and all-red light is 1-α(%) and 1-β(%), respectively. Also, by setting β as larger than α, the protection afforded by all-red lights would be more robust than that by amber lights.

　　Emerging from this research, which sorted through vast samples and looked into examples of past effort, were two practical courses of action for authorities to adopt in regard to signal change intervals.
Post date 2013/07/05
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