Assessing modal tradeoffs and associated built environment characteristics using a cost-distance framework

The relationship between the built environment and transportation mode choice is well-studied, but less attention has been spent on the way that urban environments influence the relative travel costs for different modes. This paper uses a 'cost-distance' framework to assess the tradeoffs between transportation modes for commuters in the Dublin metropolitan area and employs random forest models to investigate non-linearities in the relationships between relative mobility by mode and built environment characteristics. The results suggest that more 'walkable' built environments increase the efficiency of active transport modes; however, we also find that these environments are negatively related to cost efficiency for public transport, likely due to congestion effects for buses. Beyond these theoretical insights, the results also provide a spatially targeted set of priorities for policymakers looking to improve the efficiency of sustainable transportation modes. These methods could be applied to any global region with access to the requisite data.