Hang on though. ATW▸ doesn't have any HST▸ 's.
Depends what you mean by HST (yes, I know you probably mean IC125, most people do).
This page on ATW's website actually calls the class 175s 'High Speed Trains', although their top speed of 100mph isn't sufficient to meet the definition of 'high speed' for existing lines given by Wikipedia (which is 120-124 miles per hour). Interestingly I think ATW also may have the wrong engine listed on that page for their class 158s, elsewhere I've read that ATW's 158s have Perkins engines not the Cummins model listed. Even on Wikipedia's definition, ATW do in fact have HSTs, the class 67s and mrk3 stock are rated for 125mph (actually I'm not sure if the
DVT‡ is limited to 110mph or 125, although I don't think ATW use any sections of track with a linespeed of over 100mph anyway).
All that said, the rolling stock situation on Wales & Borders currently looks very difficult to resolve as I see it. Assuming Wikipedia has the fleet sizes correct, there are 12 mrk3s, 30 Pacers, 36 150s and 8 153s to deal with before the 2020 TSI-
PRM▸ deadline (the 158s and 175s are probably close to compliant, if not compliant already). Add to this that ATW's fleet is stretched fairly thin (whose isn't, apart perhaps from
SWT▸ with their ability to sublease units to other TOCs?) and trains are too short for demand in many cases. The Pacers, 150s and (in their current form, at least) 153s are in my opinion unsuitable for much of the franchise, except that 150s are ok for the ValleyLines. Then there is the further complication that the ValleyLines are supposed to receive electrification (or, god-forbid, tramification*), but it would take a miracle for this to happen by 2020. Thus we need:
- An increase in the size of the long-distance (regional express) fleet (currently 158s, 175s and mark 3s), including major upgrade or replacement of the mrk3s
- A short-term diesel solution for the ValleyLines from 2020 until electrification
- Suitable rolling stock for the rural/branch lines on the franchise (eg. Conwy Valley, Heart Of Wales and Pembroke & Tenby)
- New electric stock following valleys electrification
That last one's the easy bit, since there will probably be sufficient time to get the electric stock ordered while the wires are going up. The other three are really difficult issues.
For regional express, the only new-build option currently on the market seems to be the CAF mrk5 coaches (and are there enough spare 67s to haul them?). A
DMU▸ would be more flexible but there isn't a regional express design on the shelf and the time to develop one would probably push us beyond the 2020 deadline. Even an add-on order for more of the outer-suburban CAF DMUs** might not be deliverable by 2020. One way out of this fix could be if the rumoured use of Wessex electrics with diesel locos goes ahead. That would allow replacement of the mark 3 stock and perhaps some lengthening of Manchester services, allowing the 2-car 175s to be cascaded down the 'food chain' ending up perhaps on the Heart Of Wales to take the longest-distance use of 153s and 150s out of the equation.
The short-term diesel requirement for the ValleyLines is perhaps the hardest problem to solve, investment in TSI-PRM mods for 150s and Pacers would probably not be financially viable since they would only be useful until electrification after which they will be surplus to requirements. Converting London Underground stock into DMUs is likely to be similarly expensive for a short-term use. With the number of diagrams required on the ValleyLines, even if the stock wasn't totally unsuitable elsewhere you'd need huge growth elsewhere on the franchise to find a use for all of it.
* I actually think some light-rail conversion might be a good idea, but the hour-long journeys from the heads of the valleys to Cardiff are too long for a tram in my opinion (the only trams I have relatively recent experience of are Manchester's, which have far too few seats (and no toilets) in favour of standing room compared to the current DMUs on the ValleyLines).
** which wouldn't be much use in Wales, you could use them on Cardiff-Cheltenham, Wrexham-Bidston (unless electrification actually happens), Llandudno-Holyhead stopping services, reopened branches around Swansea and perhaps Swansea-Pembroke Dock all-stops but that's about all they would really be suitable for