Setting change intervals at signalized intersections
Timing the change interval is a complex task in traffic engineering. Even though the mathematical basis of the problem can be derived in a straightforward manner, its application is by no means as clear cut. First and foremost is the disagreement among traffic engineers from one jurisdiction to another regarding the ''correct'' way to set a change interval. Among the major differences are the use of an all-red phase and the consideration of the start-up time for cross-street traffic. Setting aside these differences, the ''dilemma'' zone of a yellow light can be eliminated - or an ''optimal'' timing can be set - by manipulating a myriad of design parameters. Chief among these are the yellow interval, the all-red phase, speed limit, pavement condition and geometrics at the intersection. Changing one of these parameters would affect the others during the design process. This ''system'' effect was dramatically illustrated by the case studies and the computer runs where a dilemma zone can be eliminated by raising the speed limit, for example, rather than lowering it as called for by the Traffic Control Devices Handbook and by ''intuition.'' The case studies also illustrated the possibility of remarking and repaving as a way to solve the problem. By reexamining the current design formula for the change interval, the authors have also shown that a dilemma zone will exist as long as one does not distinguish between perception and muscle-response time. In other words, the current design formula of lumping perception and muscle-response time in one single reaction time is to be discouraged.
- Research Organization:
- Dept. of Civil and Environmental Engineering at Washington State Univ. (US)
- OSTI ID:
- 5072340
- Journal Information:
- ITE J.; (United States), Vol. 57:2
- Country of Publication:
- United States
- Language:
- English
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