This paper analyzes trends in the technological profile of the Austrian personnel vehicle fleet from 1990 to 2007. This includes the parameters of power, engine size and weight, which beyond the technological efficiency of the motor engine itself, are considered to be the main determinants of the fuel efficiency of the average car stock. Investigating the drivers of ever rising transport related greenhouse gas emissions is crucial in order to derive policies that strive towards more energy-efficient on-road passenger mobility. We focus on the efficacy of technological efficiency improvements in mitigating climate-relevant emissions from car use in light of shifting demand patterns towards bigger, heavier and more powerful cars. The analysis is descriptive in nature and based on a bottom-up database that was originally collated for the purpose of the present study. Technological data on car models, which includes tested fuel consumption, engine size, power and weight, is related to registered car stock and, in parts, to newly registered cars. From this, we obtain an original database of the Austrian passenger car fleet, i.e. information on consumer choice of specific car models, segregated by gasoline and diesel fuelled engines. Conclusions are derived for policies aimed at reducing the fossil fuel consumption of the moving vehicle fleet in order to contribute to a low carbon society.