Traffic flow on a section of a two-lane highway can be described by the Greenshields model, with a mean free speed of 55 mi/h and a jam density of 145 veh/mi/ln. At the time when the flow was 90% of the capacity of the highway, a large dump truck loaded with heavy industrial machinery from an adjacent construction site joins the traffic stream and travels at a speed of 15 mi/h for a length of 3.5 mi along the upgrade before turning off onto a dump site. Due to the relatively high flow in the opposite direction, it is impossible for any car to pass the truck. Determine how many vehicles will be in the platoon behind the truck by the time the truck leaves the highway.

Traffic flow on a section of a two-lane highway can be described by the Greenshields model, with a mean free speed of 55 mi/h and a jam density of 145 veh/mi/ln. At the time when the flow was 90% of the capacity of the highway, a large dump truck loaded with heavy industrial machinery from an adjacent construction site joins the traffic stream and travels at a speed of 15 mi/h for a length of 3.5 mi along the upgrade before turning off onto a dump site. Due to the relatively high flow in the opposite direction, it is impossible for any car to pass the truck. Determine how many vehicles will be in the platoon behind the truck by the time the truck leaves the highway.

Traffic and Highway Engineering

5th Edition

ISBN:9781305156241

Author:Garber, Nicholas J.

Publisher:Garber, Nicholas J.

Chapter6: Fundamental Principles Of Traffic Flow

Section: Chapter Questions

Problem 21P

See similar textbooks

Similar questions

due to closure of certain lanes of a highway, the capacity is reduced to 75% of its normal capacity. If in normal capacity the jam density of the highway is 103 veh/km, and the free flow speed is 58 kph, determine what would be the maximum flow if the flow is limited to 85% of its current state.
What would be the capacity of the highway if the jam density 200 veh/km, and having a flow rate of 500 veh/hr when density is 155 veh/km
A freeway traffic stream was observed to have a density of 22.0 veh/mi/ln when the mean speed was 55.0 mi/h. On another occasion at the same location, the jam density was found to be 132 veh/mi/ln. Assume Greenshields' model of traffic flow applies. The optimum speed (in mi/h) is: a) 22.0 b) 33.0 c) 55.0 d) 66.0 e) None of he above
The lane of a 2-lane one way carriageway is closed for repairs. The maximum mean free speed under conditions of low flow in the 2-lane portion is 65km/hr. Under conditions of low flow, observations show that the maximum mean free speed in the bottleneck is also 65km/hr. The average space headway when vehicles are stationary is 12.5m. The volume of traffic on the 2-lane road is 1800 veh/hr. Assuming that the speed-concentration relation is linear, find The mean speed of traffic through the bottleneck caused by the closure of one lane; The mean speed of traffic in the congested conditions immediately on the approach to the bottleneck The mean speed of traffic on the carriageway clear of the influence of the bottleneck The rate at which the queue of the congested traffic enter
The SLEX was designed to carry a free-flow speed of 50 kph and a capacity of 4000 veh/hr. At a certain point near the intersection of a road leading to Laguna, there were 3600 vehicles counted in one hour. Assume a linear relationship. Determine the space-mean speed. Determine the jam density.
The volume at a section of a two-lane highway is 1500 veh/h in each direction and the density is about 25 veh/mi. A large dump truck loaded with soil from an adjacent construction site joins the traffic stream and travels at a speed of 10 mi/h for a length of 2.5 mi along the upgrade before turning off onto a dump site. Due to the relatively high flow in the opposite direction, it is impossible for any car to pass the truck. Vehicles just behind the truck therefore have to travel at the speed of the truck which results in the formation of a platoon having a density of 100 veh/mi and a flow of 1000 veh/h. Determine how many vehicles will be in the platoon by the time the truck leaves the highway
The volume at a section of a two-lane highway is 1500 veh/h in each direction and the density is about 25 veh/mi. A large dump truck loaded with soil from an adjacent construction site joins the traffic stream and travels at a speed of 10 mi/h for a length of 2.5 mi along the upgrade before turning off onto a dump site. Due to the relatively high flow in the opposite direction, it is impossible for any car to pass the truck. Vehicles just behind the truck therefore have to travel at the speed of the truck which results in the formation of a platoon having a density of 100 veh/mi and a flow of 1000 veh/h. Determine how many vehicles will be in the platoon by the time the truck leaves the highway. Draw the figure.
From an aerial photograph, one observes that on a level section of a (multilane) highway, 25% of the vehicles are trucks, 75% are cars, and there are 50 vehicles per mile of highway. The trucks travel at 40 mph and the cars at 60 mph. This highway also has a section with a steep grade on which the speed of the trucks drops to 25 mph and the speed of the cars to 55 mph. No vehicles enter or exit the subject highway sections (except at the ends). The flows on these highway sections are stationary, which means that the flows on the level section are equal to those on the grade. Determine (a) the flow of vehicles on the level section; (b) the density of vehicles on the grade; (c) the percent of trucks on the grade as seen from an aerial photo; (d) the percent of trucks as seen by a stationary observer on the grade.
Given a Greenshields linear density-speed relationship of us = 71.2 - 0.584k a. derive the flow-speed relationship equation b. Derive the flow-density relationship equation c. Find the mean free flow speed d. Find the jam density e.Find the capacity
A freeway traffic stream was observed to have a density of 22.0 veh/mi/ln when the mean speed was 55.0 mi/h. On another occasion at the same location, the jam density was found to be 132 veh/mi/ln. Assume Greenshields' model of traffic flow applies. The flow rate (in veh/h/ln) at the time when the mean speed was 55.0 mi/h is: 990 1210 1540 2178 None of the above
Traffic flow on a three-lane (one direction) freeway 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 2 hours. It is estimated that the capacity at the work zone will be reduced by 25 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. If it is estimated that the demand flow on the highway during the emergency repairs is 85 percent of the capacity, using the deterministic approach, determine the following. the maximum queue length (in veh) that will be formed the total delay (in h) the number of vehicles that will be affected by the incident the average individual delay (in min)
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…