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Optimisation of Area Traffic Control for Equilibrium Network Flows

Chiou, Suh-Wen; (1998) Optimisation of Area Traffic Control for Equilibrium Network Flows. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

A bi-level programming approach is used to tackle an optimisation problem for area traffic control with equilibrium flows. The signal timing plan is defined by common cycle time, and by starts and durations of green. The system performance index is defined as the sum of a weighted linear combination of rate of delay and number of stops per unit time for all traffic streams, which is evaluated by the traffic model from TRANSYT (Vincent, Mitchell and Robertson 1980). User equilibrium traffic assignment is formulated as a variational inequality problem. Approximate mathematical expressions for various components of the performance index and the average delay to a vehicle at the downstream junction in the TRANSYT model for both undersaturated and oversaturated links are considered and the corresponding derivatives with respect to signal setting variables and link flows are derived (Chiou, 1997b). The gradient projection method is used in deciding feasible descent directions. Optimal choices of step length along feasible directions for changes in offsets are particularly considered. A mixed search procedure is proposed in this thesis, in which better local optima can be found by solving the unconstrained optimisation problem with respect to the offset variables; therefore a global search for particular directions can be carried out in many parts of the feasible region. Two test road networks have been chosen to illustrate the effectiveness of the proposed method and comparisons for the values of the performance index with other conventional methods have been made. Encouraging results on the Allsop and Charlesworths road network (1977) have shown the robustness and efficiency of the proposed mixed search procedure as values of the performance index were improved in comparison with the non-optimising calculation of mutually consistent TRANSYT-optimal signal timings and equilibrium assignment.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Optimisation of Area Traffic Control for Equilibrium Network Flows
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Thesis digitised by ProQuest.
URI: https://discovery.ucl.ac.uk/id/eprint/10104576
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