Application for comparing frequency and schedule-based approaches in the simulation of a low frequency transit system

To simulate a transit system two approaches can be used: a line approach where all runs belonging to the same line are simulated in a single infrastructure line; a run approach where the single runs are explicitly simulated. Assignment models simulate how origin-destination demand flows affect link flows and resulting performances. Traffic assignment models in transit systems are generally made up by two different approaches: a frequency approach for high frequency services to simulate the user’s behaviour and considering line approach to simulate the supply; a schedule-based approach for low frequency services to simulate the user’s behaviour and considering run approach to simulate the supply. Recently the schedule-based approach has undergone great advances in terms of models, procedures and commercial software and with current performance it could also be used for simulating high frequency services. Currently, many practical applications are being developed using frequency approach, also for low frequency services. In this paper the shortcomings of the frequency approach using optimal strategy compared with the schedule-based approach are investigated in simulating extra-urban transit system in terms of user behaviour simulation and subsequently verifying a numerical application. The two approaches are applied to the extra-urban supply system of the province of Reggio Calabria. In the province there are about 570,000 inhabitants and the supply has more than 1300 runs a day. The results obtained with the schedule-based approach are discussed and compared. Pros and cons of each approach are discussed.