Effect of the Omission of Users? Costs on the Spatial Design of Public Transport Services
S Jara-Díaz, A Gschwender, M Ortega, Universidad de Chile, CL
Omitting users' time makes direct services with low frequencies a superior design in transit networks. When users? costs are included, direct services with large frequencies are more likely to be the preferred outcome if demand is sufficiently high
It has been shown recently in the literature that the presence of a stringent financial constraint translates into an implicit reduction of users? time value in the design of public transport systems, inducing a less than optimal bus frequency and larger than optimal bus size. This conclusion was achieved with a microeconomic model for a single line where space played no role. When multiple lines are allowed in the context of an urban network, different spatial pattern of services can be envisioned, i.e. direct services (no transfers) or corridors (transfers are needed).
The objective of this paper is to consider in the cost model the strategic decision regarding the spatial structure of services, in order to study the impact of neglecting users? costs (i.e. their time)on the spatial design of transit services. This is done through the analysis of four simple though illustrative networks. First, the optimal structure of lines is investigated, searching for the combination of lines, frequencies and vehicle sizes that minimize the total costs, i.e. operator?s and users?. Then the same problem is solved accounting for operators? costs only.
The results show that, when all costs are accounted for, direct services are more likely to be the preferred outcome only when, for given time values, demand is sufficiently high. When only operators? costs are considered, the preferred outcome would be direct services under all circumstances, with lower frequencies. These results are explained in terms of fleet size requirements and both in-vehicle and waiting times associated to each objective.
Association for European Transport