An optimization model for bus route redesign considering accessibility improvement for seniors

Bus transit acts as a significant catalyst in the process of sustainable and resilient urbanization. However, within any given urban agglomeration, residents do not benefit from the transit services on an equal footing. This is particularly the case for socially disadvantaged groups such as seniors, children, and low-income households. Generally, a walking distance of 400 m is used as a walkable distance threshold for bus stops in public transit design practice and age-friendly city guidelines. Unfortunately, due to irregular transit service regions or a dispersed distribution of bus stops, age-restricted communities which have become a popular residential option for older adults are not necessarily built in locations meeting the 400 m-criterion and thus provide limited accessibility to nearby bus stops. In this context, this paper aims to apply integer linear programming (ILP) to help redesign the existing bus route (or route segment) surrounding the locations of age-restricted communities in order to minimize the operation cost for transit agencies under a series of constraints including satisfying accessibility requirement of bus transit to seniors. Finally, a numerical example, based on the grid street pattern, is illustrated to demonstrate the applicability of the proposed method.