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2456. Frequency optimization in public transportation with strict capacity constraints
Invited abstract in session WB-55: Public transportation , stream Transportation.
Wednesday, 10:30-12:00Room: S02 (building: 101)
Authors (first author is the speaker)
| 1. | Antonio Mauttone
|
| Operations Research Department, Universidad de la República | |
| 2. | Agustín Arizti
|
| Universidad de la República | |
| 3. | María E. Urquhart
|
| Universidad de la República |
Abstract
The problem of frequency optimization consists in defining the number of vehicles per time unit, to operate each line of the system. The inverse of the line frequency is the time interval between consecutive vehicles in the line, which determines the waiting time. Given an available fleet and origin-destination demand data, we seek to minimize the total travel time of passengers, including in-vehicle and waiting components. To evaluate a frequency setting we apply the optimal strategies assignment model, which represents passenger behavior and outputs demand flows over the lines and passenger travel time from origin to destination. The capacity of a line is determined by its frequency and the size of the vehicles which operate the service. In systems operating over capacity, the flows produced by the assignment model exceed line capacity, causing failure to board the vehicles that passengers choose. To avoid this endogenous effect which invalidates the whole model, we propose a frequency optimization model that guarantees sufficient capacity in all lines. This is achieved by including a strict line capacity constraint in a bilevel programming model. After applying a reformulation, we obtain a mixed integer linear programming model which can be solved to optimality for small to medium size cases. We apply the model to a simple toy instance and to a well-known one, taken from literature. Numerical results allow for investigating the usefulness and the limitations of the model.
Keywords
- Transportation
- Network Flows
- Public Local Transportation Systems
Status: accepted
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