Answered: Consider the problem of traffic flow on…

Structural Analysis

6th Edition

ISBN:9781337630931

Author:KASSIMALI, Aslam.

Publisher:KASSIMALI, Aslam.

Chapter2: Loads On Structures

Section: Chapter Questions

Problem 1P

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Consider the problem of traffic flow on a three-lane (one direction) freeway which can be described by the Greenshields model. One lane of the three lanes on a section of this freeway will have to be closed to undertake an emergency bridge repair that is expected to take several hours. It is estimated that the capacity at the work zone will be reduced by 28 percent of that of the section just upstream of the work zone. The mean free flow speed of the highway is 60 mi/h and the jam density is 140 veh/mi/ln. It is estimated that the demand flow on the highway during the emergency repairs is 86 percent of the capacity.

Using the deterministic approach, determine the following for the expected repair periods of 1 h,1.5 h,2.5 h,2.75 h, and 3 h.

(a)

the maximum queue length (in veh) that will be formed

(b)

the total delay (in h)

(c)

the number of vehicles that will be affected by the incident

(d)

the average individual delay (in min)

(e)

Plot a graph of average individual delay versus the repair period.

(f)

Use this graph to discuss the effect of the expected repair time on the average delay.

Consider the problem of traffic flow on a three-lane (one direction) freeway which can be described by the Greenshields model. One lane of the
three lanes on a section of this freeway will have to be closed to undertake an emergency bridge repair that is expected to take several hours. It is
estimated that the capacity at the work zone will be reduced by 28 percent of that of the section just upstream of the work zone. The mean free flow
speed of the highway is 60 mi/h and the jam density is 140 veh/mi/In. It is estimated that the demand flow on the highway during the emergency
repairs is 86 percent of the capacity.
Using the deterministic approach, determine the following for the expected repair periods of 1 h, 1.5 h, 2.5 h, 2.75 h, and 3 h.
(a) the maximum queue length (in veh) that will be formed
1 h
1.5 h
2.5 h
2.75 h
3 h
(b) the total delay (in h)
1 h
1.5 h
2.5 h
2.75 h
3 h
(c) the number of vehicles that will be affected by the incident
veh
1 h
1.5 h
veh
2.5 h
veh
2.75 h
veh
3 h
veh
(d) the average individual delay (in min)
1 h
min
1.5 h
min
2.5 h
min
2.75 h
min
3 h
min
3
(e) Plot a graph of average individual delay versus the repair period.
Average Delay (h)
2
O
1
Average Delay (h)
0.6
0.5
0.4
0.3
veh
veh
veh
0.2
0.2
veh
veh
0.1
h
h
h
h
h
1
0.4
LU
Repair Period (h)
0.6
2 3
Repair Period (h)
4
(i
Average Delay (h)
0.6
0.5
0.4
0.3
0.2
0.1
Average Delay (h)
3
1
2
1
2
0.2
3
0.4
4
Repair Period (h)
0.6
Repair Period (h)
(f) Use this graph to discuss the effect of the expected repair time on the average delay.
O The increase in expected repair time causes an increase in average delay; the relationship is linear.
O The increase in expected repair time causes a decrease in average delay; the relationship is linear.
O The increase in expected repair time causes an increase in average delay; the relationship is not linear.
O The increase in expected repair time causes a decrease in average delay; the relationship is not linear.
Ⓡ

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