Investment in an accessible multimodal active network: How project life cycle and investment horizon can impact the design

Abstract

The negative social and environmental impacts of car-oriented road designs have led transport policymakers to concentrate on alternative modes of travel in their recent development plans. However, in this paradigm shift, they must deal with the challenge of allocating limited resources to non-car users of transport networks in the most efficient manner. In this study, we address the resource allocation problem to maximise the accessibility of active modes on a multimodal network, accounting for the comfort of car and bus users, from a cost-benefit analysis (CBA) perspective. A bilevel optimisation model is developed in which, at the upper level, a planner moderates the network configuration by making investments in bus frequency and bike lane development to maximise the accessibility of the cycling mode over a pre-determined investment horizon and project life cycle considering a budget constraint containing operating and long-term funds. A combined modal split and traffic assignment (CMSTA) problem is considered at the lower level. The bilevel problem is converted to a single-level non-linear optimisation model by implementing KKT conditions. In a nutshell, our analysis shows that when the project life cycle is less than the planner's investment horizon, having the option to modify the design throughout the horizon (dynamic designs) leads to higher average accessibility levels compared to static designs where that option does not exist. Furthermore, charging users to use the network regardless of the link type they choose provides cyclists with higher accessibility levels. Finally, difference in value of time among users can negatively impact accessibility of cyclists.