Assessment of delivery models for semi-flexible transit operation in low-demand conditions

Semi-flexible transit (SFT) service pattern coupled with real-time dynamic scheduling of passenger requests and dynamic route assignment of vehicles is considered as a cost-effective alternative to serving public transportation users in low demand conditions. Transit agencies tend to provide SFT by delivering it in-house by public transit agencies or contracting-out to private operators like transportation network-, taxi- or microtransit companies. Past studies focussing on economic issues in implementing SFT delivery models mostly used rudimentary information provided by transit agencies to quantify the operating cost, including budgetary inputs such as average annual maintenance, fuel, and administrative costs. These aggregate costs imply a uniform cost for SFT operation per unit time; however, the cost is subjected to change through spatial and temporal variations in demand and service. This study developed analytical disaggregate operating cost models that could account for marginal variations in cost due to the change in demand and service characteristics. Such model can assist policymakers while evaluating the economic feasibility of SFT delivery models. Rigorous and approximate operating cost models are developed for two competing service patterns: commonly adopted fixed-route bus transit (FRBT) and proposed SFT. Assuming in-house delivery of FRBT, SFT operating cost Eq.s are derived for two service delivery models, namely Contract-Out Taxi, and In-House Transit. Subsequently, these cost models are used to identify the critical passenger demand, where service patterns or delivery models could replace one another to minimize the total cost of operation. Study models can be used as part of a decision support tool to establish contracting, planning, and operating policies to optimize SFT operation subjected to required service quality.