There is a growing body of research which explores the scope for applying cleaner and renewable fuels to the transport sector, with much attention focused on biofuels. Examples include:
Woods, J and Bauen A. (2003). "Technology Status Review and Carbon Abatement Potential of Renewable Transport Fuels in the UK", DTI New and Renewable Energy Programme, Department for Trade and Industry.
"Critical Issues in Decarbonising Transport: The Role of Technologies" by Katharina Kroger, Malcolm Fergusson and Ian Skinner (IEEP), Tyndall Centre Working Paper No. 36, May 2003.
Both these papers are attached below.