More roads? Infrastructure elasticities and requirements to reduce passenger transport energy demand

Increasing road capacity often leads to smaller than anticipated congestion reductions. This is due to induced demand, whereby new infrastructure stimulates travel behaviour changes. Induced demand is well documented for driving and roads, but has not yet been compared across all infrastructure types. Here, we develop an econometric regression model to estimate infrastructure-induced demand elasticities across all transport modes in the United Kingdom. Subsequently, we determine optimal infrastructure configurations for reducing energy use, constrained by costs, deployment rates, and reasonable mobility levels. Dedicated bicycle and light rail infrastructure should be prioritised, with no new roads required. Increases in energy use can be limited to 9 %, despite 12 % increases in overall mobility by 2060. Further energy savings can be achieved through reducing individual mobility demand, increasing deployment rates and encouraging new cycle infrastructure uptake, so that inelastic responses to new active and public transport infrastructure do not diminish potential energy savings.