Building on previous research, we further develop a theoretical framework for transition analysis. In particular, we are interested in the forces that guide the direction of change. We differentiate between exogenous and endogenous change where the latter can be described by the cumulative build-up of stocks and structures, which create path dependence, within a socio-technical system. Using this theoretical framework we discuss the relationship between different emerging technological alternatives to an incumbent technology, their competition and co-evolution, and their roles as bridges and dead-ends in a transition process. We then describe and analyse an early period of an ongoing transition in the road transport sector: the history of alternative transport fuels in Sweden 1974 to 2004.