Traffic and Highway Engineering
5th Edition
ISBN: 9781305156241
Author: Garber, Nicholas J.
Publisher: Cengage Learning
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Chapter 8, Problem 16P
To determine
Using Webster methods for intersection determine suitable signal phasing system and phase length.
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Task 3: The Intersection design
a. Describe the various principles involved in the design of at-grade intersections and the different types of at-grade intersections. Also, give an example of an appropriate location for the use of each type.
b. Design a suitable signal phasing system and phase lengths for the intersection using the Webster method. Show a detailed layout of the phasing system and the intersection geometry used for the geometric and traffic characteristics shown in table 6 below. And the saturation flow of the intersection is shown in table 7 Discuss the effect of increasing saturation flow rates by 10% higher on the cycle length?
Table 6:The geometric and traffic characteristics of the intersection
Approach (Width)
North (56m)
South (56 m)
East (68m)
West (68m)
Peak hour approach volumes
Left turn
133
73
168
134
Through movement
420
373
563
516
Right turn
140
135
169
178
Conflicting pedestrian volumes
900
1200
1200
900
PHF
0.95
0.95
0.95
0.95…
For the traffic characteristics and signal phasing system shown below, determine suitable phase lengths for the intersection using the Webster method. For each approach, assume one dedicated left-turn lane, one through lane, and one through-right lane.
A simple four-legged intersection needs a fixed-time signal. The critical lane flows in the N-S and E-W directions are 950 and 600 veh/hr/ln, respectively. Saturation flow is 1,950 veh/hr/ln and the lost time per phase is 6 seconds. Assume yellow interval is 3 seconds and all red interval is 2 seconds. Determine the cycle length and the distribution of green using Webster’s method.
Chapter 8 Solutions
Traffic and Highway Engineering
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