Allocating city space to multiple transportation modes: A new modeling approach consistent with the physics of transport

A macroscopic modeling approach is proposed for allocating a city’s road space among competing transport modes. In this approach, a city or neighborhood street network is viewed as a reservoir with aggregated traffic. Taking the number of vehicles (accumulation) in a reservoir as input, we show how one can reliably predict system performance in terms of person and vehicle hours spent in the system and person and vehicle kilometers traveled. The approach is used here to unveil two important results: first, that restricting access to a city’s congested areas can improve mobility for all travelers; and second, that dedicating street space to more sustainable modes like buses can improve accessibility for all modes, even if space is taken from cars. In this way, we show that this reservoir approach can determine the level of accessibility that can be sustained by a city of given structure, and can furnish insights into how city space should be allocated between various modes to improve accessibility for all travelers. We end the paper by discussing the value of expanding the approach so that neighborhood street networks can be modeled using systems of multiple, multimodal reservoirs.