Large trucks (Articulated trucks, the things that Americans call 'semis' I think) account for maybe 20% of vehicles, but about 80% of road transport greenhouse gas emissions (or figures of that order). Some smaller rigid trucks have been successfully electrified (Smith Electric Newton for example), but as yet it seems that battery-electric Articulated trucks are not being developed. Why is this? Is there some basic law of physics (size v weight v power v battery size) that makes a Battery Electric Truck (BET?) impractical, or is it cost, or infrastructure ... or what? I'd have thought that a BET would be attractive to a haulage operator on commercial grounds - cheaper to run, cheaper to maintain, longer lasting. So why are none of the big truck companies developing one? Or have I just missed it? I've seen (Seimens I think) demonstrate trucks with pantographs much like a tram, that charge on the move. But that would require substantial infrastructure spend. Given the rigid organisation and route management haulage companies apply, I would have thought that chargers at a haulage base station would work well. Battery swapping would also be an easy task - most of those places have forklift trucks. Or are large trucks the one practical application of a hydrogen fuel cell?