[en] This publication is based on a research thesis on energy transition in transports. The author proposes an analysis which aims at detailing modalities and measures which are necessary to reach the factor 4 objective (a 75 pc reduction of French greenhouse gas emissions between 1990 and 2050) in transports. The author examined the different types of scenarios of energy transition in transports and their results, and evolutions and measures which are foreseen in these scenarios to reach this objective. The author first describes the present situation of transports and mobility, and the challenges there are facing (issues of climate change and oil dependence, brief discussion of other externalities). Scenarios are then compared in terms of methodology, of scenario type, and of results. In the next part, he proposes a critical discussion of measures and evolutions which are foreseen in transports for the studied scenarios. He also reports a study of the impact of these measures by using a model of distribution among RER (suburban trains) and car. Some recommendations are finally stated for scenarios of energy transition in transports