Transit Equilibrium Assignment based on Optimal Strategies: An Implementation in EMME/2

  e have shown that it is possible to implement a true equilibrium transit assignment within the framework of the standard EMME/2 system. A variant of the macro outlined above is being used at London Transport for modeling crowding in the London Underground. Instead of using one of the default congestion functions which are based on nominal capacity, the macro has been modified for taking into account the actual profile of train density and passenger load during peak period. The details of this project are described in Abraham and Kavanagh (1992). [Page]

It can be argued with good reason, that the modeling congestion should be done using asymmetric congestion functions, e.g. as the perceived frequency of a line for a boarding passenger depending on the number of passengers already on board, or the dwell time of a line at a node depending on the number of boarding and alighting passengers. While it is indisputable that such phenomena occur in reality, including them into assignment models as the one described here unfortunately leads to models with non-unique solutions. Since the uniqueness of the solution is a primordial requirement for any assignment model, such asymmetric models, even those for which convergent algorithms are available, are of very limited practical use.

References

1

Abraham H. and Kavanagh C. (1992). Modelling Public Transport In-vehicle Congestion Using EMME/2 Release 5. Paper presented at the 1st European EMME/2 Users Conference, London, April 1992.

2

Frank M. and Wolfe P. (1956). An algorithm for quadratic programming. Nav. Res. Logist. Q. 3, 95-110.

3

INRO Consultants Inc. (1992). EMME/2 User's Manual.

4

Spiess H. (1984). Contributions à la théor

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