Heinz Spiess
EMME/2 Support Center, Haldenstrasse 16, CH-2558 Aegerten, Switzerlandheinz@spiess.ch
June 1993
Abstract:
The standard transit assignment offered in EMME/2, which is based on optimal strategies, does not consider congestion effects due to limited vehicle capacity. This assignment model can be extended by taking into account the vehicle capacity by means of a volume-dependent transit time function, leading to the formulation of a transit equilibrium assignment model. In this note, we describe how the standard version of the EMME/2 Transportation Planning Software can be used to solve this assignment model. A macro has been written which implements a Frank-Wolfe descent algorithm, by combining the fixed cost transit assignment module with the network and matrix calculator modules.
Contents
- Introduction
- Fixed Cost Assignment Model
- Transit Assignment with Non-Linear Cost Functions
- Implementation in EMME/2
- Conclusions
- References
Introduction
In most transit assignment applications, congestion effects due to overcrowding of the vehicles are not taken into account for modeling of the route choice. This is a reasonable approach in all those cases where the goal of the planning process is to provide enough capacity for all transit passenger on the routes of their choice. There are, however, situations in which it is not feasible to provide enough transit capacity to preclude congestion. In these cases, the route choice of the transit passenger is likely to be influenced by the congestion on board the vehicles, so that some travelers will switch from congested to less congested routes, even if the latter are less attractive in terms of travel time or cost.
