# Traffic Engineering Questions and Answers – Greenshield’s Macroscopic Steam Model

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This set of Traffic Engineering Multiple Choice Questions & Answers focuses on “Greenshield’s Macroscopic Steam Model”.

1. What does macroscopic stream models represent?
a) Change in behaviour of one parameter with respect to another
b) The flow density
c) The maximum passengers the vehicle can accommodate
d) The characteristics of vehicles with respect to pedestrians

Explanation: The macroscopic stream models state how one parameter’s behavior changes according to another parameter in traffic flow. The most important relationship that this model caters to is the speed and density relation.

2. What type of relationship did Greenfield assume in the speed and density relationship?
a) Elliptical
b) Linear
c) Exponential
d) Parabolic

Explanation: The type of relationship Greenfield assumed in the speed and density relationship was a linear relationship. Speed of the vehicle tends to decline as the flow rates increases. Drivers slow down when there is higher density to maintain what they perceive to be safe operations.

3. Which of the following given options shows the correct relationship between speed and density according to Greenshield’s model?
a) v = vf + (vf/kj).k
b) v = vf – (vf/kj).k
c) v = vf / (vf/kj).k
d) v = vf * (vf/kj).k

Explanation: v = vf – (vf/kj).k is the correct relationship between speed and density according to Greenshield’s model. He assumed in his model that the speed and density have a linear relationship.

4. What is the shape of the relationship between flow and density according to Greenshield’s Model?
a) Linear
b) Parabolic
c) Elliptical
d) Exponential

Explanation: The shape of the relationship between flow and density according to Greenshield’s Model is parabolic. The flow(q) is equal to mean speed(v) multiplied to density(k).

Sanfoundry Global Education & Learning Series – Traffic Engineering.

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