150: Will go after the end of the current Northern franchise
153: Sometime in the early 2030's if things go well
155: As per 150's
156: Mid 2030's
158: late 2030's - 2040
159: Same per 158's via Northern or ScotRail.
I would have thought 153 replacements will be first on the list.
as of next year,these units will be unable to run(except coupled to other units,which is financial suicide for a rural route with 20-30% capacity!),and their replacements carry 50% extra tariff in terms of track access charges.
in terms of what they do(which is run a service on super sparce lines,mostly at a loss), there is a business case for making some investment now to get a unit which can basically do the same job ,but minimise the running costs.
- most rail folk won't like this bit,but there would also be a case for DOO on these lines,with a floatng RPO instead of 2 persons per train( as that equates to about £90kpa alone per unit in staffing costs to run a 153-many of which will be lucky to see that much in passenger revenue to begin with)
As we've said on here before,the 230 can do some very isolated lines, but it is not versatile enough to include branches that also have a stint on the mainline as well(which a lot of 15x will be doing regularly).Having a 230 doing this will cause havoc for timetable planners and bottlenecks galore in the field.
Branch line speeds have not changed much, but mainline speeds over the last 30 odd years since 15x introduction have increased,where even a typical mainline slow is now rated for 90/100mph running in service, so you need a replacement that can cope with that.
The new units need a bigger spectrum of operating speeds now, as well as the lowest costs.
in essence, that's why I think the 153/150 replacements need to be 90mph capable 15-17m 2/3 car super-pacers.
It doesn't need the bells and whistles like wi-fi, but at the very least it should have better designed bogies and air-con.end gangway doors will give the option of multiple running too, which pacers don't have.
there's certainly been advances over the last 30 years in bogies,transmission and engine tech which will give a significant improvement.Not just in terms of efficiency ,but also a reduction in maintainance costs.
..the best option would be to replace153/150 at the same time,with basically the same components, economies of scale to keep production and maintainance costs down etc.
so probably a 2 car set(each car powered) with a drop-in unpowered trailer car on articulated bogies would seem sensible.