Models for public transport demand and benefit assessments.

Important issues for assessment of public transport measures are how to determine the demand for each alternative public transport mode and route and how to calculate the benefits to the passengers. There are a variety of models that deal with these issues. The authors briefly describe and discuss the appropriateness of three of the most widely used types of model and compare two of them in some more detail. The first model is a simple elasticity model, which treats the demand for public transport as a function of the price and travel time of public transport, ignoring price and travel time of competing modes. The second model is the public transport assignment model, which distributes the demand for each public transport service and mode according to travel time (and sometimes price) of each service and mode. The third type of model is the random utility model. The authors concentrate here on the most widely used model, the multinomial logit model. Besides a systematic utility component, including price and travel-time components, there is a random component (disturbance term). This term includes unknown factors as unobserved attributes, unobserved taste variations and measurement errors. A basic characteristic of the multinomial logit model is that the disturbance terms are assumed to be independent and identically distributed (IID). In Section 2 the authors first introduce some basic concepts for assessment of transport demand and benefits. Sections 3-5 then describe the three types of model, their basic characteristics, and their main tasks. Section 6 summarizes the main characteristics and tasks of the three models. In Section 7 the authors introduce one assignment model and the multinomial logit model in more detail with respect to their appropriateness for route- and mode-choice modelling and for the calculation of user benefits of travel-time changes. For this comparison, simple but typical numerical examples are used. Conclusions are given in Section 8. It should be noted that this chapter is limited to issues concerning public-transport demand and user-benefit changes due to transport measures in terms of price and/or travel-time changes. It does not deal with modelling of the interrelationships between public-transport demand and future land use, income developments, choice of destination, etc.