Addressing the economic and environmental sustainability problems of today's road transport requires, inter alia, the rapid introduction of alternative, low-carbon fuels and highly efficient, low-emission powertrains. It is unlikely that the transition from oil-based fuels and conventional internal combustion engines will occur organically at the necessary rate and following an optimum path, hence policy intervention is required. However, in order to design effective policies it is essential that the potential role of the alternative technologies is understood as best as current knowledge allows. Several high-profile studies have compared the potential of alternative road transport technologies, such as hybrids, plug-in hybrids, battery electric vehicles, hydrogen fuel cells and biofuels. The studies, critically reviewed in this paper, have generated a tremendous amount of knowledge. However, we have identified limitations that should be addressed in future comparative studies. These are: a) the complexity of the passenger car market, consisting of many segments characterised by different requirements and use patterns, is not adequately represented; b) future changes in driving behaviour brought about by new policy and technology are generally not considered; c) different studies use different performance indicators for alternative fuels and powertrains, making results difficult to compare and their interpretation difficult for the non-expert. We test the effect of these limitations on the Total Cost of Ownership of each of the alternative technologies mentioned above. We demonstrate that building market segments and behavioural change into a comparative analysis significantly affects its results and we recommend that this is done in future studies.
