Sang Nguyen

A COMBINED TRIP DISTRIBUTION MODAL SPLIT AND TRIP ASSIGNMENT MODEL

Abstract We develop in this paper a trip distribution, modal split and trip assignment model. As is well known, the entropy type distribution model is equivalent to postulating a travel demand function where trips are proportional to a negative exponential function of the travel cost. We show that when two distribution models of this type are linked with route choice models based on Wardrops “user optimized” principle, the mode choice is given by a logit model. We develop a solution algorithm that computes the resulting trip interchanges and route flows.

A Modeling Framework for Passenger Assignment on a Transport Network with Timetables

This paper presents a new graph theoretic framework for the passenger assignment problem that encompasses simultaneously the departure time and the route choice. The implicit FIFO access to transit lines is taken into account by the concept of available capacity. This notion of flow priority has not been considered explicitly in previous models. A traffic equilibrium model is described and a computational procedure based on asymmetric boarding penalty functions is suggested.

Implicit Enumeration of Hyperpaths in a Logit Model for Transit Networks

This paper investigates the application of a logit model to urban transit networks where every set of competitive transit lines is described by a particular graph structure called hyperpath. It shows that a sequential form of the logit model transcends the inherent limitations of the global form while retaining the algorithmic advantages similar to those obtained with the ordinary logit model for private vehicle networks.

Route Choice on Transit Networks with Online Information at Stops

Passengers on a transit network with common lines are often faced with the problem of choosing between either to board the arriving bus or to wait for a faster one. Many assignment models are based on the classical assumption that at a given stop passengers board the first arriving carrier of a certain subset of the available lines, often referred to as the attractive set. In this case, it has been shown that, if the headway distributions are exponential, then an optimal subset of lines minimizing the passenger travel time can be easily determined. However, when online information on future arrivals of buses are posted at the stop, it is unlikely that the above classical assumption holds. In this case, passengers may choose to board a line that offers the best combination of displayed waiting time and expected travel time to their destination once boarded. In this paper, we propose a general framework for determining the probability of boarding each line available at a stop when online information on bus waiting times is provided to passengers. We will also show that the classical model without online information may be interpreted as a particular instance of the proposed framework, this way achieving an extension to general headway distributions. The impact of the availability of information regarding bus arrivals and that of the regularity of transit lines on the network loads, as well as on the passenger travel times, will be illustrated with small numerical examples.

Modeling Bus Stops in Transit Networks: A Survey and New Formulations

In this paper, we undertake a detailed study of the bus stop problem in congested transit networks. In the first part of the paper, we present and discuss the bus stop models existing in the literature. In the second part, we propose a new general model for which we prove a number of good properties and we give equivalent formulations. Then, we examine two special cases of the general model. In the first case, the line capacities are considered limited and therefore they can not be exceeded by the on-board passenger flows. In the second case, the strict capacity constraints are relaxed in order to obtain a stop model that can be easily integrated into an assignment model to predict the global passenger behavior in transit networks.

A dual simplex algorithm for finding all shortest paths

We present an adaptation of the dual simplex algorithm, for computing all shortest paths on a network. Given a shortest path arborescence rooted at node r, the change of root to a new origin s, renders the arborescence rooted at r dual feasible and primal infeasible for the new problem. The adaptation of the dual simplex algorithm to compute the shortest paths from node s results in an algorithm which has the flavor of a label-setting method. It generally does not require the examination of all the nodes of the network. We report some computational results with the method which indicate that it is at least as efficient as successive applications of a label-setting or a label-correcting shortest path algorithm.

Recent Experience with Equilibrium Methods for the Study of a Congested Urban Area

We report in this paper on the application of the algorithm of Nguyen [1], that computes network equilibrium flows, to assign peak hour traffic on the road network (1971) of the City of Winnipeg, Manitoba.

EMME: A planning method for multi-modal urban transportation systems

The purpose of this paper is to present a new multimodal urban transportation planning method, EMME (Equilibre Multi-Modal/Multi-Modal Equilibrium), that is based on and is consistent with a general theory of equilibrium in transportation systems. The requirement that is often asked of transportation systems analysis methods is that they be policy responsive, in the sense that a considerable number of the variables considered are explicit policy variables: changes in these variables bring about changes in the distribution of transportation demands and flows between origins and destinations, over specified links, between modes or by time of day. EMME has been designed to respond, as much as is possible within the current state of the art of transportation systems modelling, to changes in these variables and is oriented to short term and medium term planning applications. The implementation of EMME exploits the considerable progress that has been achieved recently in the development of efficient algorithms for the computation of equilibrium flows in transportation networks and on advanced concepts for computer based systems and data bank design.