Arriva Cross-country often have a Voyager in one of the centre roads at Birmingham New Street, and presumably have a crew ready to work it if needed. This strikes me as a sensible idea, but I can't think of any other examples bar the Clapham Junction yard HST during the recent Great Western diversions. How much does it cost to actually provide such a unit, presumably the crew will be rostered along with the other diagrams, having a spare unit to keep as a hot spare is a luxury many TOCs don't have though. Surely such things could be specified in franchise agreements, certainly in the long-term a spare TPE unit would be useful at Leeds, or failing that at York Leeman Road? Thoughts?