Bilevel Decision-Support Model for Bus-Route Optimization and Accessibility Improvement for Seniors

Bus route networks play a pivotal role in public transit system planning, which, in turn, influences the geographical distribution and service coverage of bus transit. Although some advanced approaches have been applied to optimize route network planning, transit-related social exclusion still exists for particular socially disadvantaged groups, such as seniors. Furthermore, because transit agencies are generally the primary decision makers in conventional route optimization, the leading decisions may not favor the interests of transit users. In this study, an optimization methodology for bus route redesign is introduced in order to facilitate transit operation management and enhance the benefits that seniors receive from transit services. A bilevel decision support model (BLDSM) for two schemes is formulated for the identified problem. In the proposed model, transit agencies, as lower-level decision makers, locate appropriate bus stops and generate bus routes using the shortest distance as an optimization criterion. Meanwhile, decisions with regard to providing maximum accessibility to seniors as the upper-level decision makers are taken into account. To address this problem, a location-routing-allocation strategy is proposed and implemented in Scheme I using exact methods, and, in Scheme II, exact methods are integrated with a genetic algorithm (GA) in order to identify a near-optimal solution. A numerical example is provided to assess the feasibility of the proposed method for the two schemes. A discussion of what might happen if the roles of transit agencies and seniors were adjusted in the built BLDSM is also included.