This project emerged from The Department of Transport’s need to increase the number and quality of transport evaluations. To do this, a better understanding of how to attribute impacts to transport polices and schemes was required.

Attribution can be addressed in more than one way. Depending on their circumstances, transport schemes may be better evaluated through an experimental approach or a theory based approach. This project aims to identify what these circumstances are; to help analysts choose the right approach and achieve better attribution in impact evaluations, and consequently improve understanding of the impacts of transport polices, programmes, and schemes. The main output from this work will be a set of guidelines which will take readers through a six-step process to help them identify the most suitable evaluation approach for the intervention they are looking to evaluate.