To contribute to a sustainable society, considerable reduction in energy use and CO2 emissions should be achieved. This paper presents the results of calculations exploring the energy use reduction potential of passenger transport for Western Europe (OECD Europe minus Turkey). For these calculations, three types of options are defined emphasizing technological, infrastructural and behavioural change. By 2050, technological improvements may reduce energy use per passenger-km by similar to 30%. Adding infrastructural options, an energy reduction of > 50% by 2050 can be realised. To achieve further energy reductions, options with a large behavioural impact should also be implemented. This results in an 80% energy reduction potential in the transport sector by 2050. To calculate the reduction potential on OECD Europe level, one should factor in expectations concerning mobility growth. Two mobility development scenarios are used. Both scenarios foresee a net decrease in total energy use of 20% with the introduction of the technological and infrastructural improvement options. Adding options emphasizing behavioural change results in a net reduction potential of similar to 60% by 2050.