A public transit network optimization model for equitable access to social services

TL;DR

This paper introduces a flexible transit network optimization model that improves equitable access to social services with minimal impact on costs, using a hybrid algorithm and a Chicago case study.

Contribution

It presents a novel optimization model for minor transit network modifications that enhance social equity without significant cost increases.

Findings

Improved access to primary health care in Chicago

Achieved better equity through resource reallocation

Minimal impact on existing network costs

Abstract

We present a flexible public transit network design model which optimizes a social access objective while guaranteeing that the system's costs and transit times remain within a preset margin of their current levels. The purpose of the model is to find a set of minor, immediate modifications to an existing bus network that can give more communities access to the chosen services while having a minimal impact on the current network's operator costs and user costs. Design decisions consist of reallocation of existing resources in order to adjust line frequencies and capacities. We present a hybrid tabu search/simulated annealing algorithm for the solution of this optimization-based model. As a case study we apply the model to the problem of improving equity of access to primary health care facilities in the Chicago metropolitan area. The results of the model suggest that it is possible to achieve better primary care access equity through reassignment of existing buses and implementation of express runs, while leaving overall service levels relatively unaffected.