People have been trying hydrogen. It’s generally a bit of a disaster.

And increasingly I think that is being quietly admitted. It has a weird afterlife in buses (where the range potential is interesting for long-range intercity routes), but even there, at this point, it’s marginal. The Irish transport authority placed an order a few years back for 800 BEV buses… and three hydrogen buses, for instance. A decade ago, BEV buses and hydrogen buses were both basically experimental. Today BEV buses are ordered by the thousand; hydrogen buses are still experimental.

(Also I expect hydrogen _trains_ to hang around as a concept for a while, and it _may_ actually be viable there where adding overhead lines is not.)

> It would allow legacy vehicles to stay on the road

How? Hydrogen cars _are electric cars_; they just have a fuel cell instead of a battery. If you’re imagining that they have, er, a four stroke engine that they burn hydrogen in or something, yeah, that’s not a thing.

I suppose if you wanted to get _really_ weird you could have a hydrogen turbine car? But again, that’s nothing like current petrol cars tech (and would be horribly inefficient relative to the fuel cell ones).