09h00 - 10h00
Semi-flexible Transit Systems
When demand for transportation is low or sparse, traditional transit cannot provide efficient and good-quality level service, due to their fixed structure. For this reason, mass transit have been evolving towards some degree of flexibility. Although the extension of Dial-a-Ride systems to general public meets such need of adaptability, it presents several drawbacks mostly related to their extreme flexibility. Since the mid '90s, new transportation alternatives have been increasingly proposed, combining on-demand service adjustment capabilities to the regular route and schedule characteristics of traditional transit. Due to their twofold nature, such so-called semi-flexible systems require a very challenging planning process. In this tutorial we provide an overview of different semi-flexible systems and we show that the transit paradigm called Demand Adaptive System can be applied as a unifying model for the whole family of semi-flexible systems. Furthermore we will review the most important practical experiences as well as the main methodological contributions to the planning process. We will finally conclude by analyzing some of the open planning issues and emphasizing the need for extensive research in the field.