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A Branch-and-Bound Based Framework for Route Set Generation. Outline. Motivation and Objective Background Generate Realistic Route Set Summary Open Questions. Outline. Motivation and Objective Background Generate Realistic Route Set Summary Open Questions. Motivation and Objective. - PowerPoint PPT Presentation
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Universität StuttgartInstitut für Straßen- und VerkehrswesenLehrstuhl für Verkehrsplanung und Verkehrsleittechnik
M.Sc Yaohua XiongIDS 2012
2012.12.13
Pfaffenwaldring 7 70569 Stuttgart Tel. +49 (0)711 685-82480 www.isv.uni-stuttgart.de/vuv/
A Branch-and-Bound Based Framework for Route Set Generation
Outline
Motivation and Objective
Background
Generate Realistic Route Set
Summary
Open Questions
Outline
Motivation and Objective
Background
Generate Realistic Route Set
Summary
Open Questions
Motivation and Objective
Path Based Assignment Path Flows instead of Link Flows Detailed Result Stable Result
New Question: are the paths “realistic”? What is “realistic”? How to make paths “realistic”?
Terminology Route: Consecutive Links Path: Path + Departure Time
Outline
Motivation and Objective
Background
Generate Realistic Route Set
Summary
Open Questions
Conventional Assignment Process
A
B
Done!
Find Free Flow Shortest
Path
Network Loading
Converge?Find CongestedShortest Path
Path Flow Set
End
Start
Existing Approaches for Route Generation
Approach Procedure Result Ref
K-shortest Path Exact Deterministic Van der zijpp
Link Elimination Heuristic Deterministic
Azevedo et al.
Gateway Heuristic Deterministic Lombard
Labeled Heuristic DeterministicBen-akiva et al.
Monte-Carlo Heuristic Stochastic Ramming
Additional Approach
Outline
Motivation and Objective
Background
Generate Realistic Route Set
Summary
Open Questions
What is a Realistic Route (Set)?
Route that travelers are willing to use “Subjective” Not Operative
“Objective” and Operative Definition Coverage Rate Estimation Quality
But the definition of “realistic” route *is* subjective No Physical Rules
Solution: Ask “What is an unrealistic route?” Use Intuition Formalize the Rules The Rules are called Constraints
Subtraction Approach
Branch-and-Bound
Branch: systematically enumerate all pathsBound: eliminate unrealistic paths
Non-Cyclic Constraint
No Cycle in Route
Detour Constraint
No Excessive Detour
Detour Factor = Path Length / Shortest Path Length
(Local) Detour Constraint
Turn Constraint
Without C(8,4) = 70 C(18, 9) = 48620 C(38, 19) = 35345263800
With e.g. max_turn = 1
NNNNEEEE
EEEENNNN
ENENENEN
Other Constraints
How to identify new constraints?
Use Intuition Researcher Expert Opinion Survey
Road Hierarchy
Distance Matters
Road Hierarchy Aware Enumeration
Determine Access and Egress Point
Generate Sub-routes from origin to Access Point
Generate Sub-routes from Egress point to Destination
Generate Sub-routes from Access Point to Egress Point
Concatenate Sub-routes
Choice Set Composition
Choice Set vs Route Set
Post Process Individual Avaibility/Perception Overall Quality Control
Outline
Motivation and Objective
Background
Generate Realistic Route Set
Summary
Open Questions
Summary
OD PairGrouping
Enumeration
End
Start
RH AwareEnumeration
Constraints
Composition
Subtraction Instead of Addition. Non-cyclic Constraint Detour Constraint Turn Constraint Others...(Use the
intuition, Luke)
Road Hierarchy Aware Enumeration
Composition
Overall Framework Route Set Generation
Constrained Path Based Assignment
Converge?
Path Based Assignment ConstrainedPath Based Assignment
Find Free Flow Shortest
Path
Network Loading
Converge?Find CongestedShortest Path
Path Flow Set
End
Start
RouteEnumeration
Network Loading
Find ConstrainedShortest Path
Path Flow Set
End
Start
Open Question
With a given link impedance definition CPBA is not necessarily achieve equilibrium.(shortest path will not be considered due to constraints)
Equilibrium Assumption is True
Constraints are Valid
Why?
→ The impedance has latent factors which are not took into account in the current definition?
A
B
