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Traffic Signal Systems Operations and Design: Isolated Intersections
5. Which maximum green time setting would you select and why?
6. Identify the pros and cons of the two different maximum green time settings on the westbound approach
and on the overall performance of the intersection. Consider what you observed and documented for
both cases. Summarize the pros and cons of each case.
In this activity, you will observe two cases, each focusing on the westbound approach of the major
street, State Highway 8 (See Figure 149). In the first case, the maximum green time is set to 40
seconds. The demand is relatively high (1700 vehicles per hour across two lanes) on the westbound
approach and the green time displayed is not sufficient to serve the demand. In the second case, the
maximum green time is set at 60 seconds in an effort to serve more of the demand. But this change
also has implications that must be considered for the operation of the intersection. Each case includes
four cycles, focusing on the westbound approach. You will be asked to look at three things:
•
What is the length of the queue at the beginning of each of the four green intervals on the westbound
approach?
•
How does the westbound phase terminate during each of the four cycles in each case?
•
Are there vehicles from the westbound queue still unserved at the end of the green interval?
Figure 149.
Activity 42 movie file
A
ctivity
42: D
etermining
the
E
ffect of
the
M
aximum
G
reen
T
ime on
I
ntersection
O
perations