The TDNS was about the best way to decarbonise.
Kind of; obviously it wasn't just what was technically the best option (otherwise it would be electrification everywhere, except perhaps the odd seldom-used route where the carbon savings on the operations side are outweighed by the maintainance and construction of the electrification infrustructure). Still, surely the key thing should be getting the routes where electrification is clearly the best option (ie. those identified as 'core electrification' by the TDNS) done ASAP?
I was dead against bimodes at first and now I realise they are useful for similar reasons.
There are bi-modes and bi-modes. I can't remember what my original stance on regional bi-modes was, but I have always been dead against 125mph (and above) bi-modes because the routes they run should be way up the priority list for electrification. I will admit that even the class 80x/810 units have proved useful but, with enough diesel engines under the 80x/810 fleet to power around 200 such units, I think we have plenty of those now. I am however currently in favour of procurement of new lower-speed bi-modes (90-110mph), particularly regional express units (444 alikes) for the likes of Waterloo-Exeter. Indeed, since the publication of the TDNS I have been strongly of the view that no more single-mode units (other than straight EMUs) should ever be built for GB rail. Apparently, the 10 speculative hydrogen Aventras will be single-mode hydrogen-only units and, unless converting them to multi-mode is as simple as adding OLE compatability to a class 707 then I think this is a big mistake. Passive provision for OLE compatability has been a requirement on new third rail EMUs for many years, it's high time the same was applied to
new trains for (currently) non-electrified routes.
This. A potential bimode life of 30-50 years gives scope for a lot of wiring to happen in the meantime. Only issue is making sure we don't waste time.
Yes, bi-modes appear pretty much essential to delivery of decarbonisation as recommended by the TDNS in a sensible timeframe. My go-to example of this is Wolverhampton-Shrewsbury, which is 'core electrification' but the case for wires would be weakened substantially if the units used on the Cambrian lines (where TDNS recommends hydrogen) lack OLE compatibility, unless you fancy angering the local user group by terminating their trains at Shrewsbury. Another angle on this is that having the busy part of a long route wired helps with the range issue - if you have a multi-mode train you can conserve battery-charge/hydrogen-stocks while under the wires rather than 'burning' it under the wires. So yes, bi-mode is a useful concept but can we have it more on regional units now please? InterCity has enough of 'em, get wiring.