Consistent delays at Cambridge South: What improvements could be made to resolve these?

[Tobzere]

Hello,

As Cambridge South has now been open a couple of weeks, I was hoping that by now the services would be relatively reliable.

I am a user of this station, to reach Meldreth. This service is constantly delayed, often by 20 Minutes, with some trains being outright cancelled last minute, both Northbound and Southbound.

I understand there have been some issues with the trains, and several are out of service due to having extra maintenance after the Pantograph issue the other week.

My question is, if anyone with more knowledge could shed some light on the issue, and fill my confidence that it will get better in the long run.

I am very thankful for the new station, but the inconsistency and unreliability is making me second question if I should be getting the train, as I can't guarantee to be getting home in a timely manner at the moment.

Thanks

 

[Benjwri]

GTR doesn't have the best reputation for reliability but Greater Anglia is much more reliable normally. OnTimeTrains shows a reliability graph for Cambridge that shows that there has been a significant drop recently, although when it will improve is difficult to say.

 

[Starmill]

Performance has been poorer than usual across Great Britain unfortunately and this line has definitely not done well out of it.

It's likely that it will tick back up again a little as there is some time for repairs to the trains, and there are fewer days with temperatures higher than average for this time of year. Performance can also struggle a little during the leaf fall period though.

 

[Ashfordian6]

Any late arrival from Ely into Cambridge now seems be causing trains to quickly start backing up in the area because of the complication of needing to now stop at Cambridge South.

I suspect it is going to take a few iterations of small timetable changes to smooth this out so that backlogs do not so easily occur at Cambridge/Cambridge South.

 

[dk1]

Hasn’t it always been like that with GN/Thameslink?

 

[wagnaga]

Any late arrival from Ely into Cambridge now seems be causing trains to quickly start backing up in the area because of the complication of needing to now stop at Cambridge South.

I suspect it is going to take a few iterations of small timetable changes to smooth this out so that backlogs do not so easily occur at Cambridge/Cambridge South.

Was this actually just being masked previously by the timetable having the time allowance for the stop built in for months before opening?

 

[rmHawk765]

It is not really down to the station. My first guess would be the above about time allowances. Essentially when the station was being built every train already had the stop in the timetable but every train also skipped the station (or occasionally used it to overtake) so in effect trains could run slightly early.

Additionally the Cambridge & Fen lines have suffered from consistent delays particularly in the peak ever since the Dec 2025 timetable was introduced, often down to 12-coach trains not splitting/joining in time at Cambridge. And the ECML's reliability recently has been overall horrific. The timetable has prioritised IC services over everything else and the Cambridge & Fen GN timetable is now fundamentally broken. There are infrastructure upgrades that should have been done years ago but will seemingly never happen, for example overtaking capability in the Royston area. The issue is that the timetable allows delays to spread extremely easily, even if the trains you get themselves do not get delayed directly.

Also, as long as Cambridge-Brighton continues to exist in its current form, there will always be knock-on delays caused by issues halfway across the southeast.

 

[RUK]

I suppose that the four-tracking around the area as part of East West Rail is intended to help with this, within about a decade’s time?

 

[dk1]

I suppose that the four-tracking around the area as part of East West Rail is intended to help with this, within about a decade’s time?

Yes, it’s around the mid 2030s that EWR is proposed to begin operation at that end.

 

[choochoochoo]

Why does the kings cross flyer need to stop at cambridge south ? There's plenty of other services between cambridge south and cambridge to transfer onto or from this service.

I'm betting it'll be one of the first stations on a not to call order in the event of disruption.

 

[dk1]

Why does the kings cross flyer need to stop at cambridge south ? There's plenty of other services between cambridge south and cambridge to transfer onto or from this service.

I'm betting it'll be one of the first stations on a not to call order in the event of disruption.

Makes sense really as it calls at the North too. It’s a very popular service with plenty of use by those at the biomedical campus.

 

[rmHawk765]

Why does the kings cross flyer need to stop at cambridge south ?

Why not? It makes no discernable difference to journey time and introduces useful connections.

 

[wagnaga]

Why does the kings cross flyer need to stop at cambridge south ? There's plenty of other services between cambridge south and cambridge to transfer onto or from this service.

I'm betting it'll be one of the first stations on a not to call order in the event of disruption.

Every train that runs through Cambridge South stops there. This is different to north where for example Cross Country don't call. It was said this was to make the timetable work.

 

[rmHawk765]

Every train that runs through Cambridge South stops there. This is different to north where for example Cross Country don't call. It was said this was to make the timetable work.

I'd imagine the difference comes from the fact that Cambridge North has no overtaking capability, but also just because South serves much more important destinations.

 

[wolveseycastle]

Why does the kings cross flyer need to stop at cambridge south ? There's plenty of other services between cambridge south and cambridge to transfer onto or from this service.

I'm betting it'll be one of the first stations on a not to call order in the event of disruption.

If the fast service from KGX wasn't to call at Cambridge South, then it would render the station partly pointless, because coming up instead on a slow to Cambridge South vs coming up on a fast to Cambridge and then getting the bus back down the busway or Hills Road to the Biomedical campus would be quite close timewise. Obviously that's not the only interesting passenger flow but is an example.

 

[Jim the Jim]

The fast trains to King's Cross are also King's Lynn -- Cambridge stoppers, and I imagine have quite a few people on them from the north who would like to go to Cambridge South.

The Crosscountry trains stopping at South but not North seems arbitrary to me.

 

[Royston Vasey]

The fast trains to King's Cross are also King's Lynn -- Cambridge stoppers, and I imagine have quite a few people on them from the north who would like to go to Cambridge South.

The Crosscountry trains stopping at South but not North seems arbitrary to me.

They always had plenty of marginal time between their departure times at Stansted and Cambridge. They had (and still have) generous pathing time at Audley End and a sparse service to fit around up to Shepreth Branch Jn. I believe their dwell time at Cambridge used to be four minutes before departing on the hour, and is now three, but I could be wrong. They still depart Cambridge to Birmingham on the hour.

Have they been retimed departing Stansted? I don't recall the previous timings!

Going the other way, they have a long turnaround at Stansted and the CMS stop doesn't add more than a minute or so (linespeed there was slow before the station arrived)

I expect a stop at Cambridge North would be lot more disruptive to pathing, particularly up through Ely.

 

[Magdalia]

Why does the kings cross flyer need to stop at cambridge south ?

For journeys between Kings Lynn line stations and Cambridge South.

There is also travel from London to the Biomedical Campus, including some commuting.

 

[Starmill]

The Crosscountry trains stopping at South but not North seems arbitrary to me.

Why? The stop at Cambridge North would need the train to leave Cambridge main earlier, which would be almost impossible as it's on the minimum margin with the London-bound train at Shepreth Branch Jn. Southbound there is sometimes more time to play with at Cambridge main, but generally stopping would knock the other London express which is already right behind.

South was also vastly easier to fit within platforming at both Cambridge stations because they sacrificed Audley End from having a through service to Peterborough etc, or more than 1tph to Stansted Airport (except one a day when other services aren't running).

That leaves only the option of a swap of two Cambridge stops, but clearly it wouldn't make any sense to stop at North but not at South. They could try to alternate stops, but clearly that also increases risk. If the XC were an EMU it'd probably work, but unfortunately it's a not especially high-performing DMU.

 

[Tobzere]

It is not really down to the station. My first guess would be the above about time allowances. Essentially when the station was being built every train already had the stop in the timetable but every train also skipped the station (or occasionally used it to overtake) so in effect trains could run slightly early.

Additionally the Cambridge & Fen lines have suffered from consistent delays particularly in the peak ever since the Dec 2025 timetable was introduced, often down to 12-coach trains not splitting/joining in time at Cambridge. And the ECML's reliability recently has been overall horrific. The timetable has prioritised IC services over everything else and the Cambridge & Fen GN timetable is now fundamentally broken. There are infrastructure upgrades that should have been done years ago but will seemingly never happen, for example overtaking capability in the Royston area. The issue is that the timetable allows delays to spread extremely easily, even if the trains you get themselves do not get delayed directly.

Also, as long as Cambridge-Brighton continues to exist in its current form, there will always be knock-on delays caused by issues halfway across the southeast.

Thank you everyone for your responses, it has been very informative.

This makes sense, ever since they added the extra peak time services on the stopping trains, we have noticed that general reliability seemed to have dropped off, with the updated timetable in Dec 2025. It is getting to the point the delays are so long that they are overlapping to the next train, leading to the initial train to be cancelled. Anecdotially, towards the tail end of last week general reliability seemed a little better, with delays closer to 6-8 minutes and only cancelling two trains each day. (Although any trains cancelled is a failure imo). I would much rather less trains, but a more reliable service, than the promise of X number of trains but with severe delays.

On a side note, with all these extra trains, the downtime at Foxton Crossing is getting laughable given how vital the A10 is for Ambulances etc to get from Addenbrookes to the A1, they are having to wait for 10-15 minutes sometimes. It is about time a more long term solution was implemented with EWR, or a Harston bypass. But this is going off on a tangent to the initial thread.

 

[Starmill]

I forgot to mention March, which is very poorly served in general (though a lot better than Soham). People in March are a lot better off with a through service to South than North.

 

[bramling]

Hello,

As Cambridge South has now been open a couple of weeks, I was hoping that by now the services would be relatively reliable.

I am a user of this station, to reach Meldreth. This service is constantly delayed, often by 20 Minutes, with some trains being outright cancelled last minute, both Northbound and Southbound.

I understand there have been some issues with the trains, and several are out of service due to having extra maintenance after the Pantograph issue the other week.

My question is, if anyone with more knowledge could shed some light on the issue, and fill my confidence that it will get better in the long run.

I am very thankful for the new station, but the inconsistency and unreliability is making me second question if I should be getting the train, as I can't guarantee to be getting home in a timely manner at the moment.

Thanks

There’s a whole thread on this.

However the basic issue is that Fen Line services are prone to being delayed by other services between Hitchin and Cambridge, due to the difference in stopping patterns. A late running northbound service then encounters other bottlenecks, Cambridge station, Ely North Junction, and worst of all the single-line sections between Littleport and Kings Lynn. This then transmits late running to southbound services, which in turn makes it more likely they pick up more late running between Cambridge and Hitchin. Add to this that there isn’t much turnround time at both ends, so no real scope for delays to ride themselves out.

It got worse in December, as previously most Fen Line services interworked with the stopping services. So a late incoming Fen Line service would impact a Cambridge or Letchworth stopping service instead. From December most Fen Line services are self-contained, so they are now bearing the full brunt of everything.

There have been a lot of infrastructure and other issues recently which have worsened things, but the basic issue will still remain even if things go through a better patch.

Apparently GTR have been considering longer turnrounds at Kings Lynn, which will help a bit, but still doesn’t really address the root issue. What this will mean is that they will be able to prioritise keeping southbound services on time, but at the expense of piling delay onto northbound ones. Expect to see some very late arrivals into Kings Lynn.

 

[Flywaver1]

Why? The stop at Cambridge North would need the train to leave Cambridge main earlier, which would be almost impossible as it's on the minimum margin with the London-bound train at Shepreth Branch Jn. Southbound there is sometimes more time to play with at Cambridge main, but generally stopping would knock the other London express which is already right behind.

South was also vastly easier to fit within platforming at both Cambridge stations because they sacrificed Audley End from having a through service to Peterborough etc, or more than 1tph to Stansted Airport (except one a day when other services aren't running).

That leaves only the option of a swap of two Cambridge stops, but clearly it wouldn't make any sense to stop at North but not at South. They could try to alternate stops, but clearly that also increases risk. If the XC were an EMU it'd probably work, but unfortunately it's a not especially high-performing DMU.

Yes the Turbostar isn't designed for frequent stops. A majority of the Diagrams at Cambridge have services being relieved in the Up direction.
So a running brake test has to be done before Cambridge South so it's pretty much 40mph tops.

 

[dk1]

GSK has just announced it is to close its Stevenage base and move around 1000 staff to Cambridge. It has commented that the draw of the Biomedical Campus there was too strong and that is now bolstered by the opening of Cambridge South Station.

 

[Magdalia]

GSK has just announced it is to close its Stevenage base and move around 1000 staff to Cambridge. It has commented that the draw of the Biomedical Campus there was too strong and that is now bolstered by the opening of Cambridge South Station.

From the pictures in the BBC News report, it looks like GSK are taking space in the Discovery Drive development, see here:

Pharma giant GSK quits Stevenage for Cambridge

GSK says the relocation will put 1,000 staff at the "heart of the UK's life sciences Golden Triangle".

www.bbc.co.uk

Pharmaceutical giant GSK has announced plans to close its site in Stevenage and move about 1,000 staff to a new research and development (R&D) facility on the Cambridge Biomedical Campus.

The company has had a presence in Stevenage for 50 years but says the new location "in the heart of the UK life sciences Golden Triangle" will "accelerate our R&D and help us deliver new, competitive products".

Staff will move in phases, with the Stevenage site earmarked for closure in 2029.

Five years ago, GSK announced plans to expand its Stevenage site, with Wood claiming: "Our goal is for Stevenage to emerge as a top destination for medical and scientific research by the end of the decade."

Now, it seems the draw of Cambridge is too strong. Bolstered by the newly opened Cambridge South Station, with direct services to Stevenage, the company says it hopes "most of its staff will move with them".

 

[dk1]

From the pictures in the BBC News report, it looks like GSK are taking space in the Discovery Drive development, see here:

Pharma giant GSK quits Stevenage for Cambridge

GSK says the relocation will put 1,000 staff at the "heart of the UK's life sciences Golden Triangle".

www.bbc.co.uk

Yes that’s what I saw on the BBC Beds/Bucks/Herts report. Thanks.

 

[RUK]

From the pictures in the BBC News report, it looks like GSK are taking space in the Discovery Drive development, see here:

Pharma giant GSK quits Stevenage for Cambridge

GSK says the relocation will put 1,000 staff at the "heart of the UK's life sciences Golden Triangle".

www.bbc.co.uk

Yes - the Cambridge Biomedical Campus web-site news article says that they’ll be in 2000, 3000, and 4000 Discovery Drive. The extant 1000 Discovery Drive was also developed by Prologis, who are doing this for GSK.

I wonder what the future plans for Addenbrooke’s will be? It’s not the newest hospital, so will presumably need replacing in the not-too-distant future, within about 20 years. Presumably they will need to build a new hospital while the current one is still in use, and then move over. I can’t think of enough space on the currently-developed site for an entirely new hospital. It seems that it’d make more sense to me, or be easier, to build an entire new hospital at once (as with Papworth), rather than starting the building piece-meal, demolishing a part of it and building a replacement for that part, and working your way along the existing building. The main part is mostly a single big building now anyway. All the main buildings on the Biomedical Campus are connected by tunnels underground. The future plans for land to developed on the Biomedical Campus site to 2050 are to the south of the current site. Perhaps I’m wrong about some of my assumptions.

I suppose they have some lower-density buildings behind and to the North of the current hospital - the small tower blocks as nurses’ etc. accommodation, the Frank Lee Leisure & Fitness Centre, and the oval circular green space between those and the Jeffery Cheah Biomedical Centre and the multi-story car park could be replaced elsewhere (despite some young trees planted there), the old MRC LMB, now the University’s Clifford Albutt Building, and maybe the NHS Blood and Transplant building and the Ambulance station could be demolished and replaced by buildings elsewhere as well. The Deakin Centre and the Keith Peters Building are relatively new, so I guess they’d want to work around them. The space available looks smaller than the current hospital, though. The University are already planning to redevelop the Forvie Site.

This would mean that Addenbrooke’s would become further from/divorced above ground from the Rosie Maternity Hospital, though.

 

[Magdalia]

I wonder what the future plans for Addenbrooke’s will be?

Early thinking on this was done last year see here:

New £2.3bn hospital plans for Cambridge 'ambitious but necessary'

NHS trust says the plans for Cambridge are necessary to deal with the projected population growth.

www.bbc.co.uk

Plans for a new £2.3bn acute hospital for part of Cambridgeshire seeing rapid population growth have been described as ambitious but necessary.

Cambridge University Hospitals NHS Foundation Trust (CUH), which operates Addenbrooke's Hospital, says that by 2040 it will need double the number of beds it currently has, and an emergency department five or six times the size.

Part of the phase 2 land that is still not developed is provisionally for hospital related use. Thinking of an acute hospital with a helipad on the roof could give you a clue where it might go.

The problem is funding, it will be one of the pressing issues for the Development Corporation when it starts work.