Traffic and Highway Engineering
5th Edition
ISBN: 9781305156241
Author: Garber, Nicholas J.
Publisher: Cengage Learning
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Chapter 6, Problem 9P
To determine
Optimum speed and optimum density if the traffic stream is modeled using Greenberg model and free flow speed, optimum speed and optimum density if the traffic stream is modeled using Greenshields model.
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A linear relationship is observed between speed and density on a certain section of a highway. The
free flow speed is observation to be 80 km per hour and the jam density is estimated as 100 vehicles
per km length. Based on the above relationship, the maximum flow expected on this section and the
speed at the maximum flow will respectively be
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
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
Chapter 6 Solutions
Traffic and Highway Engineering
Ch. 6 - Prob. 1PCh. 6 - Prob. 2PCh. 6 - Prob. 3PCh. 6 - Prob. 4PCh. 6 - Prob. 5PCh. 6 - Prob. 6PCh. 6 - Prob. 7PCh. 6 - Prob. 8PCh. 6 - Prob. 9PCh. 6 - Prob. 10P
Ch. 6 - Prob. 11PCh. 6 - Prob. 12PCh. 6 - Prob. 13PCh. 6 - Prob. 14PCh. 6 - Prob. 15PCh. 6 - Prob. 16PCh. 6 - Prob. 17PCh. 6 - Prob. 18PCh. 6 - Prob. 19PCh. 6 - Prob. 20PCh. 6 - Prob. 21PCh. 6 - Prob. 22PCh. 6 - Prob. 23PCh. 6 - Prob. 24PCh. 6 - Prob. 25PCh. 6 - The arrival times of vehicles at the ticket gate...Ch. 6 - Prob. 27P
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- Using Greenshields' model, for a highway with a mean free flow speed of 76 mi/h and jam density of 128 veh/mi, determine the density (in veh/mi) when the mean speed is observed to be 58 mi/h:arrow_forwardH.w Try only ten): 1. The flow is zero on the highway only if the density equals to zero. 2. Density is the number of vehicle passing during a given width of lane of roadway. 3. If an accident occure during the way, it could be say that it is uninterreputed flow. 4. Mobility for arterial road is grater than the mobility of local road. 5. 85 th percentile of spot speed cumulative curve represents the highway speed limit. 6. One of the most important of on street parking is mechanical garage. 7. As angle of parking increase, more accidents would be occure. 8. At jam density, density of flow is zero. 9. PHF of rural region is less than the PHF in urban region. 10.Stopping time delay occure ar intersection. 11.Future traffic includes only generated and developed traffic. 12.As the tunover duration of the parking increase, operation of the parking increases also.arrow_forwardOn a specific westbound section of highway, studies show that the speed-density relationship is: It is known that the capacity is 5200 veh/h and the jam density is 310 veh/mi. What is the a.) space-mean speed of the traffic at capacity, (mph) b.) and what is the free-flow speed? (mph)arrow_forward
- An accident occurs on a one-lane highway and blocks off all lanes of traffic. This freeway has a jam density of 130 veh/mi. Before the accident occurred (and upstream of the queue that forms), traffic was (is) traveling at an average speed of 45 mi/h and density of 30 veh/mi. Assume that the following conditions are present: ● ● Before the queue: Uupstream = 45 mi/h, kupstream = 30 veh/mi After the queue: Udownstream = 60 mi/h, kdownstream = 0 veh/mi Jam Density: kj = 130 veh/mi How long is the queue after 25 minutes?arrow_forwardStudies have shown that the traffic flow on a 2 lane highway adjacent to school can be described by the Greenshield's model. A length of 0.50 km adjacent to a school is described as a school zone and operates for a period of 25 minutes just before the start of school and just after the close of school. The posted speed limit for the school zone during its operation is 21 kph. Data collected at the site when school zone is not in operation show that the jam density and mean free for each lane is 119 veh/km and 65 kph respectively. If the demand flow on the highway at the time of the operation of the school zone is 95% of the capacity of the highway, calculate the following: 2.1 Traffic shockwave created by the operation of the school zone 2.2 The queue length of vehicles affected by the school zone operation 2.3 The number of vehicles affected by the school zone operation 2.4 The time the queue of vehicles takes for it to dissipate after the operation of the school zone 2.5 Plot the…arrow_forward..Average free flow speed and the jam density observed on a road stretch are 60 km/h and 120 vehicles/km, respectively. For a linear speed-density relationship, the maximum flow on the road stretch (in vehicles/h) is_arrow_forward
- 7.11 A four-lane highway has a free-flow speed of 100 km/h and the flow-density relationship shown below. (1) Plot the relationship between flow and density. From this equation, determine (2) the flow capacity of the highway. Calculate (3) the jam density and (4) the speed at capacity and determine (5) the level of service when the highway is at capacity. q=100k-0.5k² lutionchin shown below.arrow_forward2. Data obtained from aerial photography showed six vehicles on a 600 ft – long section of road. Traffic data collected at the same time indicated an average time headway of 4 sec. Determine (a) the density on the highway, (b) the flow on the road, and (c) the space mean speed. Ans. k = 52.8 veh/mi, q = 900 veh/h, SMS = 17.0 mi/harrow_forward.) A study of freeway flow at a particular site has resulted in a calibrated speed- density relationship as follows: V=57.5 (1-0.008 D); From this relationship, Find the free flow speed and the Jam density. Derive equations describing flow versus speed and flow versus density.arrow_forward
- Problem 6 Traffic on a single-lane urban street observes the following flow-density relationship: q=30k(1-k/180), where q is the traffic flow in vehicles per hour (VPH), and k is the traffic density in vehicles per mile (VPM). Answer the following questions: a. | Calculate the free flow speed, capacity, and jam density of the traffic flow. b. What is the minimum spacing and the minimum (time) headway of the traffic flow? What is the traffic volume when the travel speed is 20 MPH? C.arrow_forward9. A segment of a highway was designed for a free flow speed of 90 mph. At the time of observation along the segment, it was recorded that same segment was at its maximum flow. What is the average speed of vehicles at this instant? a) 60 kph b) 45 kph c) 55kph d) 75kph 10. In Problem 9, what is the density of vehicles at maximum flow? a) 1/3 jam density b) 1/4 jam density c) 1/2 jam density d) none of thesearrow_forward4. When the accident rate (instead of accident number) is used to identify hazardous location, there is bias towards selecting low-flow locations with few accidents. A. True B. False 5. If all cars on one lane move at 25 mph and all cars on the second lane move at 30 mph, the time mean speed and space mean speed calculated for the 2-lane highway will be the same: Α. True B. False 6. Free-flow speed is the speed at maximum vehicle flow rate for the Greenshield's speed- density relationship: Α. True B. Falsearrow_forward
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