In many economies, motor fuel taxes have long been the main instruments for generating tax revenues from the transport sector. Nowadays they are also rationalized on the grounds of reducing congestion, carbon emissions, local air pollution, energy dependency, and sometimes accident costs. However, for several reasons, there is now much debate about reforming or partially replacing these taxes. This debate raises several kinds of research questions, including efficient design of such tax instruments and what factors affect their design in reality, CTS organised an international symposium where recent research regarding these issues was presented. This report summarises some findings from the symposium.