Global emissions scenarios studies, such as those informing the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5), highlight the importance of the transport sector for climate change mitigation—along with the difficulties of achieving deep reductions therein (1) [supplementary materials (SM)]. Transport is responsible for about 23% of total energy-related CO2 emissions worldwide (2). The sector is growing more rapidly than most others, with emissions projected to double by 2050.

Transport is a fast growing sector. A steadily increasing motorization along with urbanization is a trend that can be observed in most developing countries. This and the oil dependence of the transport sector lead to considerable growth rates of carbon emissions. Actions to stop this trend are urgently needed.