Introduction to Transport. Lecture 4 : Signal Timing. Signal Timing Designs. Development of a phase plan and sequence Timing of yellow and all-red intervals for each phase. Determination of cycle length. Green time distribution. Checking pedestrian crossing requirements.
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Lecture 4:Signal Timing
A “ring” of a controller generally controls one set of signal faces. Thus, while a phase involving two opposing through movements would be shown in one block of a phase diagram, each movement would be separately shown in a ring diagram.
[vO: Opposing flow volume; NO: Opposing no. of lanes]
This RT phase may be inefficient if only one direction has a lot of RTs.
Leading green for EB RT
Lagging green for WB RT
compound phase if RTs are permitted.
The intergreen time is,
x: safe stopping distance
L: vehicle length
v: Vehicle legal speed
This part is the length of the all-red interval.
This part is the length of the yellow interval.
Other criteria based on local policies may be applied, and several phase plans may be tested.
determine the desirable cycle length based on a desired vlc (0.85-0.90) ratio and the PHF
Note that the procedure recommended does not yield a unique result, nor does it allow for development of an initial signal timing entirely by algorithm. The traffic engineer must apply some judgment in the process, and should be aware of applicable local or regional policies that may affect the process. The resulting signal timing is only the INITIAL TIMING.
Finding actual green interval values (Gi):
Gi = gi – Yi + tLI