Repeat Problem 8-16 using pedestrian flow rates that are 20% higher. What effect does this have on cycle length?
What will be an ideal response?
Assume the following saturation flows:
Through lanes: 1600 veh/h/ln
Through-right lanes: 1400 veh/h/ln
Left lanes: 1000 veh/h/ln
Left-through lanes: 1200 veh/h/ln
Left-through-right lanes: 1100 veh/h/ln
Step 1: Calculate equivalent hourly flows
Step 2: Assume an intersection configuration, assign lane groups, and determine
critical volumes.
In this case, each approach was assumed to have one dedicated left-turn
lane, one through lane, and one through-right lane.
Sum Yi = 0.770
Step 4: Calculate lost time per cycle, using Equation 8.8
Assume lost time per phase due to acceleration and deceleration at phase changes
is 3.5 seconds and that an all-red interval of 1.5 seconds is provided at each phase.
Total lost time, L = 20 sec.
Step 6: Allocate green times
Allocated times are for green and yellow indications; appropriate length of
yellow interval can be subtracted from the total to give green times.
Total effective green time, Gte = C – L =135 seconds
(G+Y)1 = (0.177/0.770)(135) + 3.5 = 34.5 seconds
(G+Y)2 = (0.257/0.770)(135) + 3.5 = 48.5 seconds
(G+Y)3 = (0.140/0.770)(135) + 3.5 = 28.0 seconds
(G+Y)4 = (0.196/0.770)(135) + 3.5 = 37.9 seconds
Step 7: Ensure that green time required for pedestrian movement is provided,
using Equation 8.12.
Gp1 = 3.2 + (56/3.5) + (0.27)(1440/3600)(155) = 35.9 seconds
Gp2 = 3.2 + (56/3.5) + (0.27)(1440/3600)(155) = 35.9 seconds
Gp3 = 3.2 + (68/3.5) + (0.27)(1440/3600)(155) = 39.4 seconds
Gp4 = 3.2 + (68/3.5) + (0.27)(1440/3600)(155) = 39.4 seconds
Since Gp1 > (G+Y)1 , Gp3 > (G+Y)3 , and Gp4 > (G+Y)4 , the allocated sum
of green and yellow time should be 35.9 seconds for phase 1, 39.4 seconds for
phase 3, and 39.4 seconds for phase 4. Times are typically rounded up to the next
whole seconds; therefore, sum of green and yellow times are: G1 = 36 s; G2 = 49
s; G3 = 40 s; G4 = 40 s,
resulting in a total cycle length of C = (36 + 49 + 40 + 40) + (4)(1.5) = 171
seconds.
By increasing conflicting pedestrian volumes by 20%, the recommended
cycle length increased by 3.6% (from 165 seconds to 171 seconds).
You might also like to view...
Central heating systems and central air-conditioning make the growth of interior plantings easier than if they were grown outdoors
Indicate whether the statement is true or false
All of the following are common factors that influence individual ethics EXCEPT
a. family influences. b. peer influences. c. values and morals. d. situational factors. e. All of these are common factors that influence individual ethics.
A replacement plastic intake manifold may have a different design or appearance from the original factory-installed part
Indicate whether the statement is true or false
Anytime a motor has tripped on overload, the electrician should check the motor and circuit to determine why the overload tripped. The first step is generally to ____.
A. determine if the motor is actually overloaded B. put the motor back into operation C. lower the air temperature D. replace the insulation