Traffic Engineering Questions and Answers – Flow Density Relationships

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This set of Traffic Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Flow Density Relationships”.

1. Which of the following equations shows the correct relationship between flow, density, and space mean speed?
a) Flow = density/space mean speed
b) Flow = space mean speed /density
c) Density = flow x space mean speed
d) Flow = density x space mean speed
View Answer

Answer: d
Explanation: Flow = density x space mean speed shows the correct relationship between flow, density, and space mean speed. It can also be written as q = kus.

2. On which of the following factors are flow, density, and space mean speed are not dependent?
a) Characteristics of the roadway
b) Characteristics of the vehicle
c) Topography
d) Weather
View Answer

Answer: c
Explanation: Flow, density, and space mean speed is not dependent on topography. They are dependent on characteristics of the roadway, characteristics of the vehicle, weather, and characteristics of the driver.

3. With respect to the shape of the flow-density curve, when the density reaches maximum the flow must be ______
a) Maximum
b) Infinite
c) 0
d) Minimum
View Answer

Answer: c
Explanation: With respect to the shape of the flow-density curve, when the density reaches maximum the flow must be 0. This is because vehicles tend to line up end to end. Maximum density is also known as jam density.
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4. On which of the following factor does mean free speed depend on??
a) Physical characteristics of highway
b) Characteristics of the roadway
c) Characteristics of the vehicle
d) Characteristics of the driver
View Answer

Answer: a
Explanation: Mean free speed depends on the physical characteristics of the road. Mean free speed is the absolute maximum speed that is acquired when flow tends to zero. As the flow increases the speed decreases.

5. The macroscopic approach considers which of the following factor?
a) Spacing
b) Speed
c) Flow-density relationship
d) Design
View Answer

Answer: c
Explanation: Macroscopic approach considers flow-density relationship for describing traffic flow. It examines traffic streams and develops algorithms that describe the flow to the density and space mean speeds.

6. Which of the following is a model that is commonly used by the macroscopic approach?
a) Macroscopic Simulation Models
b) Mesoscopic Simulation Models
c) Greenshields model
d) Travel Demand Models
View Answer

Answer: c
Explanation: Greenshields model is a model that is commonly used by the macroscopic approach. Greenshields model hypothesized that there is a linear connection between speed and density.

7. Greenberg model uses which analogy?
a) Fluid flow
b) Laws of motion
c) Secchi disk
d) Turbidity
View Answer

Answer: a
Explanation: Greenberg model uses fluid flow analogy to develop macroscopic relationships for traffic flow. It is expressed in the following form, us = c ln(kj/k).
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8. The Greenberg model is used for which type of traffic condition?
a) Dense
b) Light
c) Uncongested
d) Unrestricted
View Answer

Answer: a
Explanation: The Greenberg model is used for dense traffic condition. The Greenberg model satisfies the boundary conditions when the density is proceeding towards the jam density. It does not satisfy the boundary conditions when density is proceeding towards zero.

9. When does the Greenshields model satisfy the boundary condition?
a) When the density is approaching zero as well as when the density is approaching the jam density kj
b) When the density is approaching infinity as well as when the density is approaching the jam density kj
c) When the density is approaching zero as well as when the density is approaching infinity
d) When the density is approaching zero as well as when the density is approaching the jam density kj
View Answer

Answer: a
Explanation: The Greenshields model satisfies the boundary condition when the density is approaching zero as well as when the density is approaching the jam density kj. It is therefore used for both light and dense traffic.
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10. The Microscopic approach does not consider which of the following factor?
a) Spacing between vehicles
b) Flow-density relationship
c) Design
d) Speed of vehicles
View Answer

Answer: b
Explanation: The Microscopic approach does not consider Flow-density relationship for describing traffic flow. The Microscopic approach is also known as car-following theory.

11. Which of the following cannot be determined by the microscopic model?
a) Velocity
b) PCU
c) Flow
d) Density
View Answer

Answer: b
Explanation: PCU (Passenger car unit) cannot be determined by the microscopic model. It is used to decide velocity, flow and density of a traffic stream when it is in a steady state.

Sanfoundry Global Education & Learning Series – Traffic Engineering.

To practice all areas of Traffic Engineering, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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