PHD Muppet (Transport Demand Modelling: Traffic Assignment)

Question 1

What are the benefits of being Robbie?

Answer 1

The list is too long for this space.

Question 2

What is User Equilibrium Traffic Assignment (UE)?

Answer 2

Aims to predict the traffic conditions on the roads, given:

• Network model
• Demand matrix, origin-destination (O-D) flows
• Volume-Delay Function

Question 3

What must UE models capture?

Answer 3

The interaction between demand and supply in the traffic networks

Question 4

What are the applications of UE?

Answer 4

• Strategic planning
• Policy analysis
• Operational Analysis

Question 5

What is System Optimal Traffic Assignment (SO)?

Answer 5

Traffic assignment models can also be used to find the best possible state of network (under full control situation), given:

• network
• Demand, OD flows, etc

SO models assume selfless behaviours and absolute compliance with instructions in favour of the system well-being

Applies to situations such as: curfew order, security matter, disaster situation, etc.

Question 6

What are the applications of SO?

Answer 6

• Identifying the best possible state of the network w.r.t given objectives (average travel time, etc)
• Evacuation management
• Travel demand management

Question 7

What is Dynamic Traffic Assignment (DTA)?

Answer 7

We know when peak hour is?

Question 8

What is deterministic?

Answer 8

Everyone acts the same?

Question 9

What stochastic traffic assignment?

Answer 9

Everyone acts differently (preferences of route).

Question 10

What are the assumptions of the Deterministic Stater User Equilibrium Assignment?

Answer 10

• Drivers have perfect knowledge of the network
• Drivers act selfishly to minimise their own travel time or generalised cost
• Temporal fluctuations in demand, congestion, and route choices are negligible

Question 11

What are the benefits of Incremental Assignment?

Answer 11

Easy and fast

Question 12

What are the disadvantages of Incremental Assignment?

Answer 12

Approximate

Question 13

What are the benefits of Method of Successive Averages (MSA)?

Answer 13

Eventually finds the equilibrium after convergence is reached

Question 14

What are the disadvantages of Method of Successive Averages (MSA)?

Answer 14

Number of iterations required for convergence and the computational time is an issue in large scale problems

Question 15

What is the basic idea of the Incremental Assignment Algorithm?

Answer 15

Assign the traffic demand to routes in incremental portions

Typically in 4 increments of 40%, 30%, 20%, 10%

Question 16

What is the basic idea of Method of Successive Averages (MSA)

Answer 16

• Assign all the traffic demand to the best route (all or nothing)
• Update the actual travel time
• Correct the assignment by re-routing a portion of the previously assigned traffic to the new best route
• Portion decreases as we go through iterations
• Continue until equilibrium is reached