I like your thinking, but I beg to differ on the CAF units being suitable, even 172's for that matter. northern has got some absolutely rotten sharp curves on it's routes.20m or less carriage length is required. I think a 17m artic like the talent would cope, but a standard 23m like a turbostar has too much swing in it. I think the maximum artic car length the UK can cope with is 18.7m like the eurostars,so for low speed rail needs to be quite a bit shorter. CAF do have an EMU with 15m artics I believe...could be an option if they can stick a power plant under it.