Module 3.2: Traffic Assignment

Question 1

What is Type 1 Traffic Assignment?

Answer 1

UE: User Equilibrium
- based on Wardrop’s equilibrium
Applications:
- strategic planning (travel demand prediction models)
- policy analysis (effects of new roadways)
- operational analysis (network performance)
E.g. congestion pricing, reversible lanes

Question 2

What is Type 2 Traffic Assignment?

Answer 2

SO: System Optimal
- best possible state of network
- assumes full driver compliance
Applications:
- contraflow
- traffic routing & controlling

Question 3

What are the 3 types of assignment algorithms?

Answer 3

1. All-or-Nothing
2. Incremental
3. Method of Successive Averages (MSA)

Question 4

What is Incremental assignment?

Answer 4

Assigns traffic demand to routes in incremental portions: 40%, 30%, 20%, 10%

Question 5

What is MSA assignment?

Answer 5

Assign the traffic demand to best route (all-or-nothing), update travel times, correct assignment by re-assigning a portion of traffic (1/2, 1/3, 1/4, 1/5 etc), continue until equilibrium reached (travel times equal for each route)