Values-of-travel time savings are widely available for use in appraisal studies, but little is known about what the consumer value is of changes in service frequency for timetable-based transport systems such as bus, train, ferry and air transport.  While values of waiting time are quoted, there are issues concerning their estimation, and for lower-frequency services travellers will adjust their schedules rather than simply waiting for the next service.  Frequency changes have an impact on benefit, but it is not clear how this should be measured.

In order to address this problem we formulate a simple demand model for timetabled transport services, considering both the generation of trips and choices among travel alternatives which include one or more timetabled services.  We use a combination of a conventional choice model (e.g. MNL) for the choice component (e.g. airline choice or train choice), and a constant-elasticity or exponential model for the generative component (numbers of trips).  Then we derive estimates of the consumer value of changes in service frequency, for instance the number of trains per hour, or the number of flights per day.  We do this by estimating the change in consumer surplus.

In our paper we use theoretical reasoning, complemented with a review of empirical aviation studies, to propose an appropriate specification of the impact of timetabled frequency and suitable parameter values for use in the choice model.  Then we illustrate the application of the method for air services, and demonstrate how the key model parameters influence the results.  The paper ends by providing some recommendations on the use of the methodology.  While the application is specific to the airline sector, the results are expected to be of interest for other long-distance transport services and possibly for other economic sectors.