Chiltern Mk5s starting 2026 - options for more capacity

[Bletchleyite]

If the sets need to be lengthened, which they probably will at some point, could they order some extra brand new MK5s from CAF to do that?

I hope they can and do… it would make things a lot more attractive for longer distance passengers.
How much money they throw at the problem though, is another issue entirely, because I’d imagine that would be the biggest limiting factor.

Given the generic press statement yesterday from GBR stating they’re going to do a renationalisation rolling stock upgrade and refresh, I would hope when Chiltern get taken back in house next year, that they are on that list.
Sadly though, SE, LNER, Northern and a couple of other TOCs seem to have a procurement process in place… which is what the DfT were getting at.
I think the 165s might be a more pressing issue for the DFTO.

Potentially one more vehicle can be added apparently.

The shuffle of other Chiltern units (above) might lead to reforms of Mk5 rakes into fewer rakes but of maximum practical length.

Apparently this is complex as it was considered initially.

The most obvious means of increasing capacity to me is to consider converting First Class to Standard when they get bored of it (as they probably will given that they did on the Mk3s) and to reseat Standard to a higher density layout with just two tables per coach in the middle where the seat direction reverses, which as the Sophia seat is still available for purchase could be done without it looking odd or without having to replace all the seats. You would get a few more rows in each coach that way without making the legroom significantly worse as it's presently a nearly-all-tables layout. It wouldn't be a great loss given that Chiltern is primarily a commuter (prefer airline seats generally) and budget (don't care as long as it's cheap) operation, and because they do short journeys the lost between-seat-backs luggage space for big bags wouldn't be a major loss. As Chiltern don't do seat reservations they could just stick a black plastic strip over the displays and pretend they aren't there rather than going to the cost of moving them.

 

[PLY2AYS]

Thanks for starting this thread. Always interesting to hear perspectives.

If it were me, I’d do something similar to GWR and put 1st class at the London end. Moves it away from the loco and you only lose half a coach to first, rather than a whole one.

If we’re talking really speculatively, I know modifications by CAF were mentioned by @MerlinRail 804 or jiggery-pokery by @Peter Sarf and if possible, add an extra standard coach loco end, or first class coach behind the DT end after the GWR style approach mentioned above.

If limited to adding just one extra coach, then make it a standard coach loco end and move the first to DT end and split the compartment of the 2nd coach to half 1st/half standard.

You’re not compromising losing any 1st custom, but you’re gaining 1 whole coach of standard.

 

[Peter Sarf]

I moved following from non-speculative thread.

If the sets need to be lengthened, which they probably will at some point, could they order some extra brand new MK5s from CAF to do that?

Potentially one more vehicle can be added apparently.

Factors would include :-

How late the decision is left. CAF, like most/all manufacturers, will not keep the capability to manufacture older designs forever (for example welding jigs). Eventually it would become too expensive.

How willing DfT are to spend on more stock.

Chiltern move on with more modern stock. There is a bigger order looming to replace the 165s. Bi Modes or Batteries are more likely to feature. Most likely generating a cascade of 168s on to longer distance (ie Mk5) workings.

The shuffle of other Chiltern units (above) might lead to reforms of Mk5 rakes into fewer rakes but of maximum practical length.

Electrification which I think can be viewed as unlikely anytime soon (done to death elsewhere on this forum).

We are most likely talking about a micro fleet that at some time in the future will be looking for a problem to solve (again).

---

Thanks for starting this thread. Always interesting to hear perspectives.

If it were me, I’d do something similar to GWR and put 1st class at the London end. Moves it away from the loco and you only lose half a coach to first, rather than a whole one.

If we’re talking really speculatively, I know modifications by CAF were mentioned by @MerlinRail 804 or jiggery-pokery by @Peter Sarf and if possible, add an extra standard coach loco end, or first class coach behind the DT end after the GWR style approach mentioned above.

If limited to adding just one extra coach, then make it a standard coach loco end and move the first to DT end and split the compartment of the 2nd coach to half 1st/half standard.

You’re not compromising losing any 1st custom, but you’re gaining 1 whole coach of standard.

It starts getting complicated when you need to re-use the existing first class coaches in other rakes. Those coaches do not have a gangway connection at one end as they couple to the loco.

BUT I think the obvious point is that these Mk5s are likely just a temporary solution (it was only a short lease iirc ?). Otherwise DfT might have entertained ideas of Chiltern juggling the formations. Instead use of the Mk5s will be on all but the busiest services to/from Birmingham with multiple 168s working the busier trains. Remember the 68s still need muzzling - I have not heard of any progress on that front ?.

So long term I see 168s cascaded in and replaced by whatever replaces 165s. All done when grossly overdue of course because easier to justify.

Thanks to @Bletchleyite for starting thread. I was about to look, unsuccessfully, for an existing one !.

 

[PLY2AYS]

It starts getting complicated when you need to re-use the existing first class coaches in other rakes. Those coaches do not have a gangway connection at one end as they couple to the loco.

I hadn’t even thought about gangway doors. What an oversight on my part! Thanks for the info.

BUT I think the obvious point is that these Mk5s are likely just a temporary solution (it was only a short lease iirc ?).

12 years wasn’t it? Not the longest lease by any means.

 

[MerlinRail 804]

One problem with lengthening them is that it reduces the options for platform sharing with say a 2 car 165 at Marylebone, which could be something that is needed more with the service increases they’ve talked. That’s something that happens a few times in the timetable I’ve designed for full Mk5 operation.
Of course that’s a whole different discussion about capacity at Marylebone and on the rest of the line though

 

[Railwaysceptic]

One problem with lengthening them is that it reduces the options for platform sharing with say a 2 car 165 at Marylebone, which could be something that is needed more with the service increases they’ve talked. That’s something that happens a few times in the timetable I’ve designed for full Mk5 operation.
Of course that’s a whole different discussion about capacity at Marylebone and on the rest of the line though

Is Marylebone the biggest capacity constraint by far on the Chiltern Main Line?

 

[PLY2AYS]

Is Marylebone the biggest capacity constraint by far on the Chiltern Main Line?

Yes, a station remodel would be helpful; but combine that with a lack of multi track layout and heritage signalling all the way along the route south of Aynho, it’s a bit of a pickle.

 

[gg1]

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It starts getting complicated when you need to re-use the existing first class coaches in other rakes. Those coaches do not have a gangway connection at one end as they couple to the loco.

How faesible/expensive would it be to retrofit gangway connections?

 

[PLY2AYS]

How faesible/expensive would it be to retrofit gangway connections?

I would imagine it would be more complicated/involved than changing the interior around.

 

[MerlinRail 804]

Is Marylebone the biggest capacity constraint by far on the Chiltern Main Line?

Defo not. At the moment it’s sort of “perfect” (while also being completely unperfect) in terms of the fact that the capacity of Marylebone matches that of the rest of the line, so to increase one you need to increase the other too really.
My timetable introduces a 2tph West Ruislip stopper into the mix, which is probably one of the biggest crunches of the whole thing

 

[mr_jrt]

Is Marylebone the biggest capacity constraint by far on the Chiltern Main Line?

I was under the impression that was one of the main selling points for the mooted OOC Chiltern platforms. Aside from them being additional terminal capacity, they can be used for the long services, freeing up the ones at Marylebone for stacking shorter services.

 

[MerlinRail 804]

I was under the impression that was one of the main selling points for the mooted OOC Chiltern platforms. Aside from them being additional terminal capacity, they can be used for the long services, freeing up the ones at Marylebone for stacking shorter services.

Surely with the OOC thing they could also extend into Paddington to be even more useful. I don’t know it that well but surely there must be some more platform capacity there thanks to the lizzie line

 

[PLY2AYS]

Surely with the OOC thing they could also extend into Paddington to be even more useful. I don’t know it that well but surely there must be some more platform capacity there thanks to the lizzie line

Think that would bring services over a different line via Greenford onto the GWML at Ealing, rather than the Neasdon South Jn/Wembley spur via the Dudding Hill Line (I think) happy to be corrected.
Both however would be a great asset for Chiltern and I’m hopeful they can both be reinstated as well as the Aylesbury spur onto East West.

Not only would that fortify/offer redundancy measures for services into London from Milton Keynes via WCML, but also offer additional commuter services for High Wycombe to MK, which currently doesn’t exist.

However this is is straying a touch too far from Mk5 territory, so I’ll stop there.

 

[The exile]

One problem with lengthening them is that it reduces the options for platform sharing with say a 2 car 165 at Marylebone, which could be something that is needed more with the service increases they’ve talked. That’s something that happens a few times in the timetable I’ve designed for full Mk5 operation.
Of course that’s a whole different discussion about capacity at Marylebone and on the rest of the line though

Should we really be spending money on increasing frequency into a London terminus if a 2 car train is going to be adequate for the flow?

 

[MerlinRail 804]

Should we really be spending money on increasing frequency into a London terminus if a 2 car train is going to be adequate for the flow?

My timetable only has the West Ruislip stoppers as 2 car (one 3 car at peak times), because that’s all it needs and the Sudburies only take 3 coaches max. The idea is that encourages more use and then the 2 car becomes not enough and you have those upgrades ready

== Doublepost prevention - post automatically merged: 11 Dec 2025 ==

My ideal dream (and kinda slightly unrealistic) world involves 4 track Wembley - Wycombe, New North Mainline reopened with services into Paddington, extension of Elizabeth line services out to High Wycombe (extend Shenfield - Paddington services with 2tph via Greenford Brand and 4tph direct to South Ruislip, with 4tph continuing to Gerrards Cross and 2 of those to Wycombe), electrfication probably of the entire line, maybe doubling Risborough - Aylesbury, and also a cheeky requadrupling of Dorridge - Moor Street or Snow Hill.
Unrealistic of course, but it’s worth throwing the idea around I guess

 

[Snow1964]

How faesible/expensive would it be to retrofit gangway connections?

Probably quite a bit. And doesn't add capacity without extra coaches or higher density seats.

But if going to spend money could probably add one of the spare mk4 coaches into the rake (between gangwayed vehicles). Probably would require change to some wiring, and maybe couplers too.

But if capacity is the requirement, might be possible to build a new basic vehicle for each set, seats full length, no toilets, and insert it between two vehicles with toilets.

 

[43096]

But if going to spend money could probably add one of the spare mk4 coaches into the rake (between gangwayed vehicles). Probably would require change to some wiring, and maybe couplers too.

Probably would require?

It would be incredibly challenging technically and prohibitively expensive.

 

[stssts1985]

Sorry if I've missed this, but surely a benefit of loco hauled rakes, is the abilty and ease by which you can increase the number of carrages - why can't they reform them into 6 carrage sets?

 

[Peter Sarf]

Sorry if I've missed this, but surely a benefit of loco hauled rakes, is the abilty and ease by which you can increase the number of carrages - why can't they reform them into 6 carrage sets?

This is the modern "improved" world I am afraid.

The Mk5s are best regarded as a multiple unit so adding or removing coaches could involve software changes maybe. It certainly involves messing around with multi way electric connectors that in the early days were not robust on the Mk5 sleepers !.

To be fair some of it is because the things are so intelligent - think power assisted doors with central door locking for instance. All controlled from one coach (I think the Driving Trailer iirc).

I think the maximum is eight vehicles in a set btw. It certainly is with the sleeper.

For long term alterations the issue came down to reforming the existing sets. One idea (on this forum) was to create 9 x 6car sets by reforming from the 13 x 5car sets. This left unused 4 Driving Trailers, 4 first class coaches and 3 second class coaches (so you could keep one 5car set). A tenth 6car set could be created by adding a declassified first class coach BUT this would need a gangway connection adding as the current first class coaches do not have a gangway connection at one end (the locomotive end).

The above is all too complicated if Chiltern are supposed to be spending the minimum. Remember if is the department for transport that controls/decides these things. The view is Chiltern were lucky to get the Mk5s.

So using all thirteen sets as five cars gives more capacity overall than making nine or ten of the sets 6car. Presumably still having to pay for any unused coaches.

 

[cle]

These will be great for Chiltern.

I expect ridership to resource once they reintroduce all their former services. There has certainly been a lot of population growth in the likes of Wycombe, Bicester and Aylesbury in the last 5 years, with much more development planned. More of the stations need TODs of various suitable types. As I agree, it’s crazy to only have 2-3 cars coming into London. The Met does a lot here of course re handling traffic.

Surely with the OOC thing they could also extend into Paddington to be even more useful. I don’t know it that well but surely there must be some more platform capacity there thanks to the lizzie line

They will be truncated bays at the western side of (likely) the northern most Crossrail platforms at OOC. I am not even sure if there is a direction connection, or straight to a dive under.

In any case, this is not planned and OOC, much like Stratford, will be a big enough hub to justify terminating services. I think the plan was 1x to each of Aylesbury, HW slow, Oxford and Banbury. That combination could well change but Birmingham is not there. So I would say maybe Marylebone’s role will be Aylesbury side and slows/fasts, with OOC for semi fasts.

It could alternatively take on slows and only run say 4tph to HW / Aylesbury if Northolt Park and Wembley picked up some calls. I would close the Sudburys.

In any case, re stacking - I can’t imagine these OOC bays will be too long. Probably a 5-6 car length and two of them.

Hopefully new no intermediate stations either (Greenford is not needed) - the Central line Ruislip branch has tons of capacity now.

Certainly while we don’t have all the answers, OOC Chiltern will see some additional capacity overall - and might just help the EWR Aylesbury service come back to life, as the rail works are being done for freight regardless.

 

[stssts1985]

This is the modern "improved" world I am afraid.

The Mk5s are best regarded as a multiple unit so adding or removing coaches could involve software changes maybe. It certainly involves messing around with multi way electric connectors that in the early days were not robust on the Mk5 sleepers !.

To be fair some of it is because the things are so intelligent - think power assisted doors with central door locking for instance. All controlled from one coach (I think the Driving Trailer iirc).

I think the maximum is eight vehicles in a set btw. It certainly is with the sleeper.

For long term alterations the issue came down to reforming the existing sets. One idea (on this forum) was to create 9 x 6car sets by reforming from the 13 x 5car sets. This left unused 4 Driving Trailers, 4 first class coaches and 3 second class coaches (so you could keep one 5car set). A tenth 6car set could be created by adding a declassified first class coach BUT this would need a gangway connection adding as the current first class coaches do not have a gangway connection at one end (the locomotive end).

The above is all too complicated if Chiltern are supposed to be spending the minimum. Remember if is the department for transport that controls/decides these things. The view is Chiltern were lucky to get the Mk5s.

So using all thirteen sets as five cars gives more capacity overall than making nine or ten of the sets 6car. Presumably still having to pay for any unused coaches.

thank you that's a really helpful reply

 

[stevieinselby]

Sorry if I've missed this, but surely a benefit of loco hauled rakes, is the abilty and ease by which you can increase the number of carrages - why can't they reform them into 6 carrage sets?

Modern carriages are different from the days of yore – for a start, there is only a very limited supply. We don't have thousands of carriages across the network that are all compatible with each other and can be pulled into new formations at will. For a start, there are only 66 Mk5a carriages (including 14 trailer cabs), so the only possible ways to lengthen trains would be (a) buying more carriages, or (ii) taking those carriages off other sets, either by short-forming other sets or dismantling some sets completely and reducing the number of services run by 68+Mk5a formations, which feels like robbing Peter to pay Paul.

But on a more general note, modern carriage sets are more connected than before. With everything being electronic and computer controlled, it isn't as simple as "just add some more carriages on". They are effectively semi-permanently coupled so can't just be shunted around and recoupled willy-nilly, but also in a lot of cases the control systems may be built in such a way that they aren't designed to be infinitely flexible. One of the carriages in each set has a blank end that faces the loco so can only be behind the loco, one of them has a driving cab and so can only be the end carriage. There may be control issues with the middle carriages if they are put together in different formations. (Think of it like 80x trains only being able to have an odd number of carriages, it isn't an intrinsic feature of MUs that they have to have an odd number of carriages, but that's how the IETs were designed. Mk5as were designed to be run as 5-car sets rather than to be swapped about).

 

[Zomboid]

Though goings on in other places show that it is possible to create a carriage which could be swapped around in the way things used to be done, that would have to be specified at the point of construction.

How are those new sets for Amtrak/ VIA set up? I think they will be used in a similar fashion to the mk5as, so they might be in fixed sets to a certain extent.

Edit:
To answer my own question, according to Wikipedia...

Most Siemens Venture cars (except those for Amtrak Midwest) are configured as trainsets, semi-permanently coupled together with wide open gangways between cars and standard couplers on the ends for connecting the trainset other railway equipment.[4]

And that's America, where they don't do MUs in the same way as we in Europe do.

 

[Instinct04]

My timetable only has the West Ruislip stoppers as 2 car (one 3 car at peak times), because that’s "all it needs" and the Sudburies only take 3 coaches max.

I would argue that hourly 2 car stoppers isn't all that West Ruislip and co stations need. But rather that is all that they are given, and with the way things are on the Chiltern lines, unlikely to change. A basic half hourly frequency would be very attractive at the ruislips, as well as Wembley Stadium.

Sorry to burst anyones bubble on this forum, but inner city commuter stations have just as much of a right to be served as outer stations do..

 

[800002]

I would argue that hourly 2 car stoppers isn't all that West Ruislip and co stations need. But rather that is all that they are given, and with the way things are on the Chiltern lines, unlikely to change. A basic half hourly frequency would be very attractive at the ruislips, as well as Wembley Stadium.

Sorry to burst anyones bubble on this forum, but inner city commuter stations have just as much of a right to be served as outer stations do..

Which is fine in principle, until it's established just how much capacity those "inner-city 'commuter stations' that are otherwise serviced by metropolitan high frequency transport (Tube and Bus)" actually eat up, thus preventing a higher frequency/ reliability of mid to long distance 'out-of-city' commuters.

 

[cle]

I would argue that hourly 2 car stoppers isn't all that West Ruislip and co stations need. But rather that is all that they are given, and with the way things are on the Chiltern lines, unlikely to change. A basic half hourly frequency would be very attractive at the ruislips, as well as Wembley Stadium.

Sorry to burst anyones bubble on this forum, but inner city commuter stations have just as much of a right to be served as outer stations do..

But they are arguably not even filling the higher frequency Central line and Piccadilly line services by them, which have capacity. Even more since Ealing went all Crossrail. And do many people even interchange at West or South from Chiltern for the Central line?

 

[172007]

Back on topic.

It would be nice for a decision to be made over the Night Riviera Sleeper Mk3 replacements and write the contract so that additional vehicles for the Chiltern Mk5 sets will be part of the contract and must be fully compatable with the Mk5a coaches.

In fact i would suggest as the Chiltern Mainline is able to take Class 165's that sleeper coachette Mk5's with the extra width could be used to reduce the cost width a little more width for comfort or luggage storage rather than Mk5A's that Chiltern currently use. Even make the new Mk5's Mark 5C's where they are wide and C3 or more longer to eke out more capacity. I immagine the GWR gauge from Paddington to Penzance both ways and via Bletchley would take longer Mk5's.