Transport is almost entirely (99.9%) powered by internal combustion engines (ICEs) burning petroleum-derived liquid fuels (95%) and the global demand for transport energy is large and is increasing. The alternatives to ICEs and conventional fuels start from a very low base and face significant environmental and other barriers to fast and unrestrained growth. For instance, there is speculation that transport could be rapidly and fully electrified. However commercial transport, which accounts for over 50% of transport energy use, is very difficult or impossible to electrify. To replace even all light duty vehicles (LDVs) by battery electric vehicles (BEVs) requires the numbers of BEVs to increase by perhaps a thousand-fold on a global scale. The greenhouse gas (GHG) impact of BEVs would be worse than that of conventional vehicles if electricity generation and the energy used for battery production are not sufficiently decarbonized. If coal continues to be a part of the energy mix, as it will in China and India, and if power generation is near urban centres, even local air quality in terms of particulates, nitrogen oxides and sulphur dioxide would get worse. The human toxicity impacts associated with battery production are large and cannot be ignored as they currently are. If governments wish to force a change to BEVs, very large investments in charging infrastructure and electricity generation will be needed. There will be additional costs in the short term associated with various subsidies required to promote such a change and in the longer term, the loss of revenue from fuel taxes which contribute significantly to public finances in most countries. Internal combustion engines will continue to power transport, particularly commercial transport, to a very large degree for decades to come and will continue to improve. There will also be a role for low-carbon and other alternative fuels where they make sense. However, such alternatives also start from a low base and face constraints on rapid and unlimited growth so that they are not expected to make up much more than 10% of the total transport energy demand by 2040. In the longer term, as GHG-free electricity generation is greatly expanded and battery technology improves there will be an increasing role for BEVs and the required charging and recycling infrastructure will evolve. Meanwhile, there will certainly be increasing electrification, particularly of LDVs in the form of hybridization to improve ICEs.