This lecture presents a study which focuses on arguably the most contentious energy supply choice for decarbonizing general-purpose long-haul road freight: hydrogen. Ten requirements for an energy supply choice to be feasible are identified. It is concluded that it is very unlikely that hydrogen will become feasible in the lifespan of a truck bought today. This means it can be disregarded as a current vehicle purchase consideration, as hydrogen vehicles will not undermine the competitiveness or resale value of a vehicle using a different energy source bought today. There are two principal innovations in the study approach: the consideration of socio-technical and political as well as techno-economic factors; and the application of realist retroductive assessment."