About fifteen years after its modest beginning, car-sharing in Germany not only makes up an important share of the transport market, it has also become firmly anchored in the sustainability concepts for the transport sector. At the same time, different signs indicate Germany's car-sharing to have reached a turning point. New techniques, new forms of offers and organisation, and the development of new groups of users might be followed by a change in the way it is used and in the emissions of car-sharing affecting the climate. This holds true both for the dominant sector of private customers as well as for company car-sharing, the line of business which is increasingly being focused on. At the end of 2001, according to the Federal Association of Car-sharing (BCS), company users made up 10 % of all users. In future many of the new private customers may see car-sharing not just as an alternative to owning a car but discover it as an opportunity to cover their desire for additional mobility. On the other hand, increased use of car-sharing by companies and organisations could make them reflect on their mobility.

Therefore, the future perspectives of car-sharing in Germany have to be reconsidered, not only regarding its market opportunities but also its climate effects. Car-sharing is not ecological as such regarding its climate effects, rather only under certain conditions.

The target of the research is an empirically based estimation of the medium-term perspectives (2020) of car-sharing in Germany for both sectors of car-sharing for private customers and for companies, its possible contribution to climate protection and its role in a sustainability strategy for transport.

Leading questions are:

• What future does car-sharing as a mobility service have on the German transport market? How far and under which conditions would a diffusion be probable?
• Which traffic-related and ecological effects are connected to car-sharing in the medium term? Will the ecological effects (on balance) more likely be positive (as before) or negative?
• Will the traffic-related and ecological effects of car-sharing in the future reach an important level according to the medium-term development of the German car fleet and the total output of motorised private transport?
• How should car-sharing be designed to increase the number of users while also ensuring that users' behaviour (on balance) remains ecological? Which frame conditions could support a process in this direction?

This project, lasting until mid-2005, concentrates on conurbations. It is being undertaken together with partners from different universities. The research team is accompanied by a council of representatives from the ministries of traffic and research, car-sharing suppliers and different associations.