An Enhanced Semi-Flexible Transit Service with Introducing Meeting Points

Semi-flexible transit (SFT) has been widely investigated in recent years and is expected to improve the balance between accessibility and operational efficiency. However, a couple of critical issues remain, such as how to develop an optimization mechanism to achieve a win-win situation for both flexible-route and fixed-route service users simultaneously, how to identify a clear service boundary between flexible-route and fixed-route service areas, and how to improve the effectiveness and competitiveness of SFT. To address these issues, this study proposes an enhanced SFT system in which meeting points are introduced to establish one flexible stop that can serve multiple users. This system can directly contribute to reducing detours, which are the main problems hindering the promotion of flexible transit services. Analytical models are derived for this optimal design, and the artificial bee colony (ABC) algorithm is adopted to solve the proposed nonlinear problem. A series of numerical cases is designed to evaluate the performance of the proposed system, which is compared with the traditional fixed-route transit and conventional SFT without meeting points. Results demonstrate that the proposed SFT achieves a lower system cost and a shorter travel time in most cases where the observed benefits vary across different factors, including demand density, average travel distance, the wealth of population, and unit length of service segment. Moreover, the introduction of meeting points helps SFT significantly reduce the routing length.