Quantifying impacts of sustainable transport interventions in Scotland: a system dynamics approach

To overcome the challenge transport presents to net zero, the Scottish Government has proposed a series of interventions to significantly reduce transport emissions and car kilometres travelled. This paper develops, validates and applies a system dynamics model of the Scottish road passenger transport sector to interrogate key proposed interventions up to 2030: namely, modal shifting sub-10km car journeys to active travel, modal shifting medium-length car journeys to buses, achieving a majority electrification of the bus fleet, and replacing 50% of petrol/diesel cars with electric vehicles. Results indicate government targets can be met, but only as a result of multiple interventions. Modal shifting of medium-length car journeys and private car electrification are predicted to be the most effective interventions for emissions reduction, although these measures alone do not attain reduction targets. Results further indicate that realising the reduction in car kilometres does not guarantee the emissions target will also be achieved.