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 Signal Timing Design: Professional Practice

 
Green Split Calculations

This excerpt was taken from the1995 Canadian Capacity Guide for Signalized Intersections, Second Edition, published by the Institute for Transportation Engineers (District 7 - Canada), (p. 58).

Green Intervals by Balancing Flow Ratios

This procedure uses flow ratios for the critical lanes. First, the total time available in the cycle for the allocation of green intervals is determined as:

Sgj = c - S Ij

Where:
Sgj = total green time available in the cycle (s)
c = selected cycle time (s) (See the explanation below.)
Ij = intergreen period following phase j (s).

This total available green time is allocated in proportion to the flow ratio of the critical lane for the corresponding phase and the intersection flow ratio:

gj = S gj (yj / Y)

Where:
gj = green interval for phase j (s)
yj = flow ratio for the critical lane in phase j
Sgj = total green time available in the cycle (s)
Y = intersection flow ratio (sum of the critical flow ratios for all phases).

(Explanation for selected cycle time)

The Canadians list several different methods for calculating the total cycle time. The engineer is supposed to select the method that suits his/her purposes best.