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3rd Civil PDF

The document contains 5 questions related to transportation engineering concepts like freeway flow, Greenshield's model, shockwave analysis, and fundamental diagrams. Question 1 asks about deriving relationships for speed, flow, and density from a given speed-density relationship and determining capacity. Question 2 involves applying Greenshield's model to given data. Question 3 asks to calculate shockwave speeds using flow, density and speed values before and after a slow truck. Question 4 is about determining Greenshield's model parameters from speed-density data pairs. Question 5 involves deriving relationships, sketching diagrams, and computing values like speed, density, headway and gaps at maximum flow.

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319 views2 pages

3rd Civil PDF

The document contains 5 questions related to transportation engineering concepts like freeway flow, Greenshield's model, shockwave analysis, and fundamental diagrams. Question 1 asks about deriving relationships for speed, flow, and density from a given speed-density relationship and determining capacity. Question 2 involves applying Greenshield's model to given data. Question 3 asks to calculate shockwave speeds using flow, density and speed values before and after a slow truck. Question 4 is about determining Greenshield's model parameters from speed-density data pairs. Question 5 involves deriving relationships, sketching diagrams, and computing values like speed, density, headway and gaps at maximum flow.

Uploaded by

Natty Tesfaye
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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ADDIS ABABA SCIENCE AND TECHNOLOGY UNIVERSITY

COLLEGE OF ARCH &CIVIL ENGG

Exercise Inst. Bulcha B .


Course: -Transport Engineering (CENG 3181)

1. A study of freeway flow at a particular site has resulted in a calibrated speed-


density relationship, as follows:

Us = 57.5(1-0.008k)

From this relationship:

a. Find the free-flow speed and jam density

b. Derive the equations describing flow versus speed and flow versus density.

c. Determine the capacity of the site mathematically

2. Inspection of a freeway data set reveals a free flow speed of 60 mph, a jam density
of 180 vehicles per mile per lane, and an observed maximum flow of 2000 vehicles per
hour. Determine the linear equation for velocity for these conditions, and determine
the speed and density at maximum flow conditions. How do the theoretical and
observed conditions compare? Use Green shield’s Model

3. A slow moving truck drives along the roadway at 10 MPH. The existing conditions on
the roadway before the truck enters are shown at point 1 below: 40 mph, flow of
1000 vehicles per hour, and density of 25 vehicles per mile. The truck enters the
roadway and causes a queue of vehicles to build, giving the characteristics of point 2
below: flow of 1200 vehicles per hour and a density of 120 vehicles per mile. Using
the information provided below, find the velocity of the shockwave at the front and
back of the platoon.

Point 1: Normal flow ( us = 40 MPH, k=25 veh/mi, q= 1000 vph.

Point 2: Slow Truck: ( us = 10 MPH, k=120 veh/mi, q= 1200 vph


4. F or the following data on speed and density, determine the parameters of the
Green shields' model. Also, find the maximum flow and density corresponding to a
speed of 30 km/hr.

k v

171 5

129 15

20 40

70 25

5. Assuming a linear v-k relationship, the mean free speed is 60 mph near zero
density, and the corresponding jam density is 140 vpm. Assume the average length of
vehicles is 20 ft. Find:

– v(k) and q(k)

– Sketch v-k, v-q, and q-k diagrams

– Compute v and k at q=1000 vph

– Compute the average headway, spacing, clearances, and gaps when the
flow is maximum

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