Traffic Flow Theory

Question 1

What is traffic flow theory?

Answer 1

Explaining traffic flow parameters in a mathematical form.

Question 2

Role of mathematic formulation

Answer 2

Is a tool in planning, design and evaluating transportation systems.

Question 3

Levels of traffic flow formulation

Answer 3

–Single vehicle (microscopic) vs many vehicles (macroscopic).
–Physical model vs empirical model
–Modeling vs simulation

Question 4

Common types of flows

Answer 4

•Unidirectional (single lane or multi-lane) flow.
–Speed, density, flow, headway)—uninterrupted flow
•Two-lane, two-way flow (uninterrupted flow)
–Gap acceptance, time delayed, flow, %directional flow, speed.
•Crossing flows (interrupted flow)
–Gap acceptance, turning flow, queue length, delay

Question 5

Fundamental Traffic Flow Parameters

Answer 5

Flow, q [veh/h] = Density, k [veh/km] X Space mean speed, Us [Km/h]

Question 6

Greenshields Model

Answer 6

Assumes linear relationship between space mean speed ( u) and density (k)

Question 7

Greenberg Model

Answer 7

Greenberg using fluid analogy and came up
with us=c ln (kj/k)
• Substituting in general equation and solving
for qmax, c corresponds to the speed at qmax.