The 317s are dreadful, only marginally worse than the 319s. Like the 319s though, I'm sure they'll be regarded by the London-based DfT as fine for carting northern peasants around.
As someone who used the 317s on a daily basis some years back, I always liked them - much nicer than either the 319s or 321s which had different seats and I never found the as comfortable.
Clearly the 317s are getting on a bit now - the oldest ones are at least 5 years older than either the 319s or 321 - and they compare poorly with modern EMUs such as the 350s.
Are they life-expired? Probably not - and enough of the 'poor old north getting old stock palmed off on them' - back in the 1980s when the DMU fleets across the north were being modernised into London's terminals you had early 1st gen DMUs into Paddington and Marylebone - carrying far more people than services to York, Leeds or Manchester were, and EMUs on the Southern dating from the 1950s.
Currently the oldest stock in regular use on the network is on London commuter routes and Merseyrail - the PEP derived EMUs - and both have plans afoot to replace.
The 319s are being set to work on a couple of very specific routes where there are no other EMUs available and despite being a similar age to the Sprinters or Pacers they are replacing, they are vastly better in terms of capacity, passenger environment and performance.
Around the general area the 319s are working you also have newer EMUs, specifically the 323s in the Manchester area and 350s operating for both TPE and London Midland serving Manchester and Liverpool respectively.
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I anticipate all the 317s to be withdrawn by 2021 with no further use to be honest. If 100mph is desired, there'll be 120 spare 321s by then which will have almost a decade on the 317s and many may well be refurbished to a high standard, some may even have been re-tractioned. If 75mph will do, the 315s are in better condition with their recent TfL refresh and to my knowledge post far better MTIN figures, are about the same age and are probably less likely to suffer corrosion issues moving forward. Failing that, I refer to the previous 321s argument.
The only possible survivors are the 317/6 fleet but again, there is just such a vast quantity of other stock ahead in the queue by that stage. it will be almost criminal to scrap even any PEP units (excluding the 508s already gone) before the Pacers, let alone Mk3 EMUs, but there's every chance it could happen if the pace of electrification continues to slacken.
A little hyperbole there - the PEP EMUs were designed for short-distance commuter services - they're unlikely to be Pacer replacements in many cases.
Two of the PEP classes are DC only - given the current standard for mainline electrification is 25kV AC, how would you propose those units were re-deployed even if electrification weren't being delayed? Clue, before you come up with a crayonista solution, don't forget the 442s are at the front of the queue for 'crazy ideas for the re-use of surplus 3rd rail EMUs'.
