Indeed. You'd have to legislate that hydrogen for vehicles could not be produced by steam reforming and add lots of regulation around tracking the origin of all

Indeed. You'd have to legislate that hydrogen for vehicles could not be produced by steam reforming and add lots of regulation around tracking the origin of all hydrogen that reaches the vehicle. Otherwise people will just use the cheapest source of hydrogen, and presuming the demand for other fossil fuels is going down at the same time, that's going to be exclusively very cheap methane feed stock.