8/6/2023 0 Comments Are traffic lights on timersSome agencies consider the pedestrian clearance interval to consist of both the FDW time and the yellow change interval. An indication warning pedestrians that the walk indication has ended and the don’t walk indication will begin at the end of the pedestrian clearance interval. Pedestrian Clearance IntervalĪlso generally known as “Flashing Don’t Walk” (FDW). Passage Time (Vehicle Interval, Gap, Passage Gap, Unit Extension)Ī parameter that specifies the maximum allowable duration of time between vehicle calls on a phase before the phase is terminated. Max OutĪ type of actuated operation for a given phase where the phase terminates due to reaching the designated maximum green time for the phase. Movement is an activity in response to a “go” (green ball, green arrow, walk, white vertical transit bar) indication. Typical movements are left, through and right. Movements can also be broken down into classes (car, pedestrians, buses, LRT, etc.). Minimum RecallĪ parameter which results in a phase being called and timed for at least its minimum green time whether or not a vehicle is present. Minimum GreenĪ parameter that defines the shortest allowable duration of the green interval. Minimum GapĪ volume density parameter that specifies the minimum green extension when gap reduction is used. Isolated intersectionĪn intersection located outside the influence of and not coordinated with other signalized intersections, commonly one mile or more from other signalized intersections. The green interval duration is controlled by a number of parameters including minimum time, maximum time, gap time, etc. The pedestrian clearance interval is determined by the pedestrian clearance time. Typically, one or more timing parameters control the duration of an interval. The duration of time during which the indications do not change their state (active or off). Gap OutĪ type of actuated operation for a given phase where the phase terminates due to a lack of vehicle calls within a specific period of time (passage time). ExtendĪ detector parameter that increases the duration of a detector actuation by a defined fixed amount. CallĪn indication within a controller that a vehicle or pedestrian is awaiting service from a particular phase or that a recall has been placed on the phase. Actuated Signal ControlĪ type of signal control where time for each phase is at least partially controlled by detector actuations. Additional terms can be found in the Glossary section of the Manual. This section identifies and describes basic terminology used within this chapter. To maximize the usefulness and transferability of the information provided, the chapter uses the terminology defined in current traffic signal control standards, such as National Transportation Communications for ITS Protocol (NTCIP) Document 1202 (1) and National Electrical Manufacturers Association (NEMA) Standards Publication TS 2-2003 (2), with alternative definitions in some cases. The principles described in this chapter are generally applicable to all signalized intersections. A major focus of this chapter is to describe basic signal timing parameters necessary to operate an intersection and guidelines for selecting values for those parameters. Signal timing is a collection of parameters and logic designed to allocate the right-of-way at a signalized intersection. This chapter documents the principles of basic traffic signal timing at an intersection.
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