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Sub-problem 2c - Page 3 of 4 |
ID# C502C03 |
Sub-problem 2c: Analyzing the Effects
of Coordination
Our task here will be
to compare these results to see which combination provides the better
overall efficiency. We can make two runs: one with all actuated movements,
arrival types of 3 and unit extension values of 3.0 seconds, and the other
with eastbound through movements and westbound through and right-turn movements
coded as pretimed, using arrival type of 4, with the unit extension values
to be ignored. The results of these two runs are presented in Exhibit 5-26
so that we can compare the affected approaches and the overall intersection
operations:
|
Exhibit 5-26. Comparison of Fully Actuated to
Semi Actuated Control |
| |
Fully Actuated |
Semi-Actuated |
|
EBT |
WBT |
WBR |
EBT |
WBT |
WBR |
|
Volumes |
670 |
597 |
178 |
670 |
597 |
178 |
|
Arrival Type |
3 |
3 |
3 |
4 |
4 |
4 |
|
Progression Factor |
1.00 |
1.00 |
1.00 |
0.24 |
0.44 |
0.44 |
|
d1 |
6.0 |
15.1 |
15.1 |
5.6 |
13.2 |
13.2 |
|
PF * d1 |
6.0 |
15.1 |
15.1 |
1.3 |
5.8 |
5.8 |
|
Unit Extension |
3.0 |
3.0 |
3.0 |
- |
- |
- |
|
k-Value |
0.11 |
0.27 |
0.27 |
0.50 |
0.50 |
0.50 |
|
d2 |
0.3 |
2.0 |
2.0 |
1.2 |
3.1 |
3.1 |
|
Movement Delay |
6.2 |
17.2 |
17.2 |
2.5 |
8.9 |
8.9 |
|
Movement LOS |
A |
B |
B |
A |
A |
A |
|
Intersection Delay |
22.0 |
16.6 |
|
Intersection LOS |
C |
B |
As you can see, the
unit extension creates k-values of less than 0.50, which lowers d2.
But, arrival type values of 3 result in progression factors of 1.00, with no
effect on d1. However, under semi-actuated control, the k-value
stays at 0.50, not affecting d2, but the progression factor is
lower which reduces the d1 term. Overall, we can see that the
combined effects of semi-actuated control on the d2 term outweigh
those of fully-actuated control on the d1 term.
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