Effect on cycle length due to
Answer to Problem 18P
Cycle length value increases with
Explanation of Solution
Given data:
Calculation:
Evaluating equivalent hourly flow −
Similarly, evaluating equivalent hourly flow for all traffic movements −
Table 1
Approach (width) | N (56ft) | S (56ft) | E (68ft) | W (68ft) |
Left turn | 133/0.95 = 140 | 73/0.95 = 77 | 168/0.95 = 177 | 134/0.95 = 142 |
Through movement | 443 | 393 | 593 | 544 |
Right turn | 148 | 143 | 178 | 188 |
Conflicting pedestrian volume | 948 | 1264 | 1264 | 948 |
Assuming lane configuration as one dedicated left turn and combined through and right lane −
Table 2
Approach | N | S | E | W |
Left | 140 | 77 | 177 | 142 |
Through + Right | 589 (442+147) | 535 (393+178) | 771 (593+178) | 730 (543+187) |
Assume a phase scheme and find critical ratios(
Table 3
- | Phase lE-W (Left) | Phase llE-W (Through) | Phase lllN-S (Left) | Phase lVN-S (Through) |
177 | 771 | 140 | 589 | |
1000 | 3000 (1600+1400) | 1000 | 3000 (1600+1400) | |
0.177 | 0.257 | 0.140 | 0.196 |
Sum of critical ratios −
Assuming lost time per phase (
So, Total lost time −
Now, determining the optimum cycle length −
(Cycle lengths are generally multiple of
Finding Total effective green time −
Effective time for phase
For Phase l
(Assuming yellow time as
For Phase ll
For Phase lll
For Phase lV
Table 4
Phase | Allocated green & yellow time (in sec) |
Total cycle length
Green time required for pedestrian crossing can be calculated as following formula:
(Assuming the crosswalk width as
Where,
Calculating
Calculating minimum time required (
Minimum time required for N approach (
Minimum time required for S approach (
Minimum time required for E approach (
Minimum time required for W approach (
Table 5
Phase | Minimum green time (in sec) |
Sum of green and yellow time is given by,
Total cycle length is given by,
Now increasing the pedestrian volume with
Table 6
New conflicting pedestrian volume | 1138 | 1517 | 1517 | 1138 |
According to the new pedestrian volume calculating minimum time required by pedestrian for each approach:
Calculating
Calculating new minimum time required (
Minimum time required for N approach (
Minimum time required for S approach (
Minimum time required for E approach (
Minimum time required for W approach (
Comparing the
Selecting greater values in between both
Table 7
Phase | New minimum green time (in sec) |
Sum of green and yellow time is given by,
Total new cycle length is given by,
Conclusion:
With using pedestrian volume flow rate
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Chapter 8 Solutions
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