Strategic measures for global ecology and security of energy supply particularly affect road traffic, as a main originator of greenhouse gas emissions by use of fossil energy. The introduction of several alternative, eco-friendly drive-train technologies in the automotitve fleet leads to a cempetition with the existing petrol and diesel engines as well as with each other. A system dynamics model is developed to understand the fundamental competing forces driving the market penetration of the new technologies, and to derive policy implications and strategies potentially contributing to their successful introduction. A conceptual model is presented to examine different diffusion patterns between competing technologies. First results show, that reaching a critical market share in time is a decisive factor. This is demonstrated for the case of Switzerland, that represents a demand driven market without an autonomous automotive industry.