# Traffic Engineering Questions and Answers – Flow Density Relationships

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

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?
b) Characteristics of the vehicle
c) Topography
d) Weather

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

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.

4. On which of the following factor does mean free speed depend on??
a) Physical characteristics of highway
c) Characteristics of the vehicle
d) Characteristics of the driver

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

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.
Sanfoundry Certification Contest of the Month is Live. 100+ Subjects. Participate Now!

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

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

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).

8. The Greenberg model is used for which type of traffic condition?
a) Dense
b) Light
c) Uncongested
d) Unrestricted

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

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.

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

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

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.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]