Highway Engineering

The Design of Highway Intersections 149

Example 5.9 Contd

Given that starting delays are 2 seconds and the amber time is 3 seconds, the
actual green time is equal to the effective green time minus 1 second:

(Minimum actual green time)N/S= 42 - 1

=41 seconds

This figure is adopted as the minimum green time for the remaining two junc-
tions within the network (A1 and A3).

Maximum actual green time:
The upper limit for actual green time at A1 and A3 is computed by con-
sideration of the minimum effective green time required by traffic at these
junctions along their east/west axis (termed side traffic):

(Minimum effective green time)E/W=(C 1 ¥ycrit(E/W)) ∏0.9

=(104 ¥ycrit(E/W)) ∏0.9

= 116 ¥ycrit(E/W)

For both A1 and A3:

ycrit(E/W) =0.444

Therefore

(Minimum effective green time)E/W= 116 ¥0.444

=52 seconds

Again, given that starting delays are 2 seconds and the amber time is
3 seconds, the actual green time is equal to the effective green time minus
1 second:

(Minimum actual green time)E/W= 52 - 1 =51 seconds

The total actual green time for both the north/south and east/west phases
is 94 seconds, estimated from the subtraction of the intergreen period
(10 s) from the total cycle time (104 s). Subtracting the minimum actual green
time along the side route from this figure yields the maximum actual
green time along the main north/south axis. Therefore, for both A1 and A3
intersections:

(Maximum actual green time)N/S= 94 - 51 =43 seconds

Minimum effective green time

seconds

()NS=¥ +

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=

96

0 363

0 363 0 474

42

.

..

Contd