Considerable efficiency gains can be made cost-effectively to set the transport sector on a sustainable development pathway. They can be achieved through already available technologies and practices, which will not only reduce greenhouse gas emissions significantly, but also generate social, environmental and economic co-benefits. However, progress in the take-up of low-carbon mobility measures substantially lags behind the potential. A number of barriers contribute to this lack of uptake. This paper explores those barriers by focusing on vehicle fuel efficiency in particular, but will also touch on the wider policy framework to improve the efficiency of the transport sector and reduce emissions. The paper suggests that a combination of fuel pricing, differentiated vehicle taxation, vehicle standards and the provision of modal choice are necessary to minimise rebound effects and significantly curb transport sector greenhouse gas emissions at low- or even negative cost.