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Chapter 7: Timing Processes for the Intersection
235
The purpose of this activity is to help you understand the role of the maximum green time in providing
efficient intersection operations. You will also validate your understanding of how to use the uniform
delay equation to determine the relationship between the delay and cycle length (and thus the maximum
green time).
•
Describe the maximum green time setting and timer process
•
Determine the optimal maximum green time (based on the optimal cycle length) at a signalized inter-
section
•
Prepare a spreadsheet with the following information:
Tab 1:
Title page with activity number and title, authors, and date completed
Tab 2:
Summary of the results of your analysis from Tasks 1 and 2 and your answers to the Critical
Thinking Questions
A model for computing the average delay when traffic is arriving at a signalized intersection at a uniform
rate was described in Activity #39. It is reproduced below. Using an Excel spreadsheet, develop a VBA
function to compute average uniform delay as a function of red time, green time, cycle length, volume, and
saturation flow rate. See the Excel Tutorial for assistance in creating a VBA function.
2
0.5 (1 / )
1 /
a
C g C
d
v s
−
=
−
Assuming a volume from one of the major street approaches of your simulation network, compute the
average uniform delay per vehicle as a function of cycle length, with a range of cycle lengths from 40
seconds to 100 seconds. Prepare a graph of delay vs. cycle length for this range of values. Assume
g/C
=
0.5 and
s
= 1900 vehicles per hour of green.
1. Prepare a brief discussion of the implications of your analysis for the maximum green time setting
for your network. What limitations exist in this analysis that must be considered when you set the
maximum green time? Include the discussion and answer in your spreadsheet.
40
What Do You Know About Maximum Green Time,
Cycle Length, and Delay?