The ECMT is currently writing a report on carbon emission reductions in the transport sector. To support this study, CE Delft was asked to write a background report on cost effectiveness of measures to reduce CO2 emissions in the transport sector. In this report, various technical mitigation options in the transport sector are analyzed: im-proved fuel economy of cars, biofuels and hydrogen. The report concludes that studies on this topic are not always in agreement. Several studies find that efficiency measures in the transport sector can be more cost effective than measures in other sectors, whereas other studies, for example a recent EEA report, disagree. Regarding biofuels, the report concludes that biomass use in power stations is more favourable from a cost effectiveness point of view. New biofuels are being developed that are expected to perform better. It is furthermore concluded that there are only very few studies available that address the issue of cost effectiveness of measures across sectors. Even data on the cost effectiveness of measures within the transport sector is scarce.