Route Alignments

Do EWR Cambridge Approaches Need 4-Tracking?

Why do we need to know about 4-tracking?

EWR Co’s decision to prioritise a southern approach into Cambridge primarily hinges on their assertion that a northern approach will require to be 4-tracked from the Milton junction with the existing West Anglia Main Line (WAML) into Cambridge. They also say that the existing Shepreth Branch Line between Hauxton Junction and Shepreth Junction (SBR) does not need to be 4-tracked but accept that this assessment needs further testing in later design stages.

Fig 1 – Northern and southern approaches into Cambridge with EWR Co’s 4-tracking proposals

It is vital that these matters are properly assessed now. To implement 4-tracking on either of these sections of existing lines would be extremely expensive. Major existing bridges would need to be modified or rebuilt and other infrastructure modified. If it is not resolved now, detailed design work would proceed based on a potentially faulty premise with the risk of locking the project into a solution that will lose valuable benefits of the alternative route.

To test EWR Co’s assessment, we have carried out our own evaluation of both their claims. We start by looking at the likely number of trains on the sections of the lines in question. We estimate the total number of trains likely to use the line including current traffic and probable growth for both passengers and freight. We discuss the likelihood of each of the scenarios occurring in practice and compare these rail traffic estimates with the capacity of the lines.


We found that EWR Co’s conclusion about the 4-tracking of the northern approach section NA2 is incorrect and that, for our estimate of the reasonable worst-case scenario, it does not need additional tracks. In fact, even with just traditional signalling there is likely to be sufficient capacity. With digital signalling, which is already specified by EWR Co, we expect there to be over-capacity.

Likewise, the southern approach section of the SBR line can probably take the reasonable worst-case passenger rail traffic estimate (which are based on Network Rail’s figures up to 2044). However, interfacing with the Thameslink services will impose severe restrictions on possible growth in traffic in excess of the figures shown due to anticipated expansion after 2044 as a result of the Ox-Cam Arc plans. The SBR line would not be able to accommodate EWR’s 6 trains per hour that are specified in the Project Wide Output Specification. The freight services estimated by Network Rail may not be able to be fully catered for because of limitations on the Newmarket line.

If EWR Co are wrong in their assertion that the SBR line does not need to be 4-tracked, the construction work that would be required exceeds the theoretical (but unrealistic) case for 4-tracking part of the northern approach.

Rail Traffic

The reasonable worst-case rail traffic scenarios for the northern and southern approaches to Cambridge are shown in Table 1. For the northern approach, we have considered the likely rail traffic on the critical section between Milton junction and Coldham’s Lane. All Newmarket trains would use platform 8 at Cambridge station enabling those services to avoid crossing movements between Cambridge Station and Coldham’s Lane. There is sufficient space in that length to increase the number of tracks should this be required.  

Table 1 – Reasonable worst-case rail traffic scenarios (trains per hour (tph) in each direction) for each approach into Cambridge

The assumptions and data sources used in compiling Table 1 are discussed below.  

  • We have not assumed any long-term change in the pre-pandemic forecasts for growth and and ‘existing’ services due to impact of COVID, even though this is likely to reduce the amount of rail traffic in the short and perhaps the medium term.
  • For consistency and independence, we have used Network Rail’s 2019 Cambridgeshire Corridor Study [Ref. 1] for assessing passenger and freight growth forecasts on the existing network for the two approaches. This will allow a fair operational comparison to be made between the approaches. We have resisted the temptation to consider in this assessment the beneficial effects (for a northern route) of an alternative future route via Newmarket for Norwich trains which has been suggested for many years, or the possibility of March trains splitting/joining other services at Ely. Combined, these could potentially reduce demand on the northern approach by 3tph. Nor have we considered the impact of a potential new Thameslink service between Cambridge and Maidstone East which may increase demand on the southern approach. Lastly, we consider that, if the Ox-Cam Arc proceeds as planned, there would be demand for even more Kings Cross services than mentioned in the Cambridgeshire Corridor Study with a timescale to 2044 only.
  • Future demand for freight on EWR is taken from a scenario suggested by Network Rail in the EWR Co’s Technical Report 3.10.7.
  • For a northern approach, EWR freight would be diverted northwards onto the WAML from Milton via a new grade-separated junction and then onto the main Felixstowe to Nuneaton freight line via a new chord just south of Ely. Any residual freight needing to pass through Cambridge would be planned out of peak hours.


Basic ‘open-track’ Assessment

In addition to the basic number of trains per hour that could use an open railway line, the capacity is affected by a number of other factors, including timetabling, any crossing movements between tracks, whether the section of track is between junctions or between stations and the mixture of freight and passenger services. We start by looking at the open-line capacity and then go on to consider these other issues.

(i) Traditional signalling

Traditional signalling systems would allow for about 15 trains per hour with no other compounding factors. This is based on international standards (International Union of Railways or UIC which is the international rail transport industry organisation); a headway (the time between trains) of 3 minutes, as convention and a minimum required by EWR Co (Technical Report Appendix B 5.7.2); and a resilience ‘safety factor’ of 0.75 (UIC Code 406 for mixed traffic lines). The reasonable worst-case scenarios for both the northern and southern approaches as shown in Table 1 appears to be within the capacity of the existing twin track based on open track conditions and traditional signalling.

(ii) Digital Signalling

However, digital signalling will be used by EWR [Ref. 2] One of the benefits of digital signalling is the additional capacity that it provides. UIC have shown that on main railway lines, the capacity increase of ETCS level 2 (with ‘block’ lengths of 400m) over ETCS level 1 could be about 37% [Ref. 3]. This is supported by a statement by Network Rail quoting capacity increases ‘of up to 40%’ [Ref. 4]. These figures should be used with care, but they demonstrate that there would be a real and significant increase in capacity. Even using a capacity increase of half of these amounts, the number of trains per hour able to be accommodated could be increased to 18 by digital signalling without the need for 4-tracking,again without any complicating location-specific issues.

Importantly, digital signalling will also allow bi-directional running on tracks. This can provide significant flexibility, especially at stations, for reversing trains.

Other Factors in Capacity Assessment

There are several factors that could reduce actual capacity on a line, including whether clock-face timetabling is used (which is it on EWR) and the number of crossing of main lines radiating from London. Below we only consider those issues that are different between approaches.

(a) The Thameslink Effect and Slow Trains

Capacity reduction can arise when other train services use the section of track and the times of those services are not possible to change. This occurs for the southern approach where Thameslink services use the track. This leads to tight and sensitive interfaces with those services. The result is that the existing 6 passenger services are almost immutable because they form part of the complex Thameslink network and the East Coast Main Line traffic. The complexity of Thameslink can clearly be seen in the map[5] below, especially all the strands of services coming together in central London where it is planned to have 24tph crossing the Thames (which, incidentally, would not be possible without the capacity-enhancing benefits of digital signalling). EWR Co are very likely to be faced with predetermined ‘paths’ (planned slots for trains) at the Cambridge end of the route that do not mesh with their required paths elsewhere. This poses a serious risk to the effective capacity of this line, the outcome of which can only be resolved when timetabling of services is attempted. This is not the case for the northern approach.

If that were not sufficiently restrictive to the timetable, this line also has a slow service calling at all stations without a ‘loop’ or overtaking section for faster trains before they reach the East Coast Main Line near Hitchin. This means that timetabling for fast trains needs to allow for these slow trains, which will lead to greater gaps between trains. There are minimal such restrictions for a northern approach.

Fig 2 – Thameslink services – note number of lines passing through central London

(b) Crossing Movements and Junctions

Crossing movements required across other tracks and junctions can also reduce the capacity of a line. In the case where junctions are flat (‘at-grade’), one train joining another line could have to wait if another train were using the section of track the first one wanted to use. ‘Grade-separated junctions’ involving ramps and bridges over lines significantly reduce this delay. The southern approach into Cambridge has two junctions (Hauxton and Shepreth Branch junctions) compared to just one for the northern approach.

The northern approach allows trains that are temporarily blocked by other trains to wait for a short time at Cambridge North station. This would allow following trains to also wait at Cambridge North (obviously on another platform) and so minimise any concertina-type delay. On the southern approach, conversely, delayed trains would have to wait in line between junctions, magnifying the impact of such a delay.

(c) Freight

Operationally, slower freight and more speedy passenger services do not mix well. Freight on a northern approach (via a new northbound chord at Milton onto the WAML and then onto the Felixstowe to Nuneaton line via another new chord south of Ely), means that freight would have no impact on EWR operations in the busy section between Milton junction and Coldham’s Lane junction. Conversely, freight and passenger traffic on a southern approach intermingle, potentially resulting in less overall capacity. If the line were eventually used for even slower moving, heavy-haul freight, such as building materials, this would only exacerbate the situation.

For a southern approach, the Cambridgeshire Corridor Study estimates that the Newmarket line, even with the anticipated dualling between Coldhams Lane junction and Teversham, could accommodate 1tph for freight during off-peak hours. Network Rail estimate the freight demand could be 1.3tph during an 18-hour window (i.e. including peak and peak hours), assuming the scenario suggested by Network Rail in the Technical Report 3.10.7. This implies that there could be insufficient capacity on a southern approach for the anticipated freight.

Another operational disadvantage of a southern approach is that because freight needs to pass through Cambridge and Cambridge South stations, the problem of platform provision in both locations would be exacerbated.

What Do EWR Co. Say?

Northern Approach

EWR Co have stated (Appendix F, 2.2.4) that the results of their analysis of a northern approach showed that there would be several conflicting movements between EWR and other services including:

  • Trains towards Ely and eastbound EWR services conflicting where EWR services join the WAML; and
  • Conflicts on various platforms at Cambridge station.

We find the first point hard to understand as there could be a grade-separated junction at Milton specifically to overcome this issue. We find their conclusion that the only remaining option is ‘to add two extra tracks to the WAML, making it a four-track railway between the new Milton junction and Cambridge station’ (Appendix F 2.2.10) curious when they could much less onerously provide a grade-separated junction at Milton than the 4-tracking option. Confusingly, they then state in Appendix F 2.2.12 that ‘a grade-separated junction is required where the EWR route joins the WAML…’.

The second point would be overcome by the construction of two more platforms at Cambridge station which EWR Co already confirm would have to be done (App F section 2.2.10). Interestingly, they fail to mention that the southern approach also needs two new platforms at Cambridge station (Technical Report 11.1.5 ). Indeed, as we will see later, there is more pressure on Cambridge station platforms from a southern approach because a freight service will need to pass through. CamBedRailRoad documents[1] provide a solution without the need for additional platforms at Cambridge.

Southern Approach

EWR Co state (Technical Report 11.4.1): ‘…it is most likely  that the SBR can remain as a twin track railway as there is sufficient existing capacity to be able to add the EWR services required to achieve the Project Objectives and leave spare capacity for an increase in services in the future.’ (Our underlining). So they have not confirmed this vital point before choosing a southerly route.

They go on to state: ‘The working assumption for the operational timetable will be assessed further in the next design phase to confirm that it is correct. The focus will be on timetable and performance modelling of the SBR to ensure that both the EWR and GTR services can run as required with suitable resilience to allow for delay, disruption, and updates to service patterns.’

They appear to acknowledge from the last statement that there could be a problem of interfacing with existing services but without being explicit about it. The Sponsor’s Requirements (App A, 5.3 and 5.4) oblige them, as far as practical, ‘to be resilient to any periods of poor performance on the wider network’ and to ‘isolate the wider network from any periods of poor performance on the Railway [EWR]’.

We consider that such a fundamental point as this should be resolved at this stage or, if it really cannot be resolved now, to base decisions on a risk-based approach (i.e. they should analyse the chances of success and the costs of each scenario) in making the choice between a northern or southern approach.

EWR Co mention that two more platforms are required at Cambridge station for a southern approach. This it is not necessarily just a case of removing some sidings to add an extra pair of platforms at the east of Cambridge station: the Royal Mail building really isn’t that far away, and may need to be removed or reduced to allow space for the extra switching tracks, particularly if another pair of side-by-side platforms are needed. Additionally, there is a very short distance between the platforms at Cambridge station and Hill’s Road bridge, in which space all the different platform tracks need to condense down to just four tracks. Indeed, that itself could become quite a bottleneck for a southern approach, as each of the various trains from London and Oxford terminating at Cambridge need to reverse & switch on their way back out.

Other Issues With Approaches

Although the above sections attempt to show whether the two approaches need to be 4-tracked, there are other arguments that need to be considered in the choice of route from a railway operations and cost viewpoint.

1. Symmetry

EWR Co state (Consultation Document page 52) that trains using a northern approach would need to terminate at Cambridge South station. Similarly, a southern approach would need to terminate at Cambridge North station since this area is also an important employment hub.

If EWR Co persist in their conviction that a northern approach would need to be 4-tracked south of Milton, a southern approach would also need to be 4-tracked to Cambridge North as it would carry at least the same amount of rail traffic. This means that, according to EWR Co’s logic, 4-tracking on this section would be needed whichever approach were adopted.

We fully understand some of the severe practical difficulties in providing this. But this underscores our assertion that the northern approach, by providing relatively easy access to all three stations in Cambridge, serves Cambridge’s employment needs better than does a southern approach.

2. Risk and Impact on Infrastructure

We have already referred to the risk of EWR Co being wrong in their future assessment of whether the Shepreth Branch line would need 4-tracking between Hauxton and Shepreth Branch junctions. If they were wrong, the structures that would require to be constructed or modified specifically for 4-tracking are:

  • M11 crossing
  • River Cam crossing
  • Widened cutting E between Cam and A1301

The first two items are major construction works in their own right.

This list is in addition to those that are required even if 4-tracking is not required, including:

  • Hauxton grade-separated junction,
  • Harston level crossing changes,
  • A1368 bridge rebuild,
  • Hauxton Road level crossing changes,
  • A1301 (rebuilt bridge likely if grade-separated junction at Shepreth Branch junction)
  • Shepreth Branch grade-separated junction.

Clearly none of these 9 structures would require to be constructed if a northern approach were adopted.

Compare this to the two structures (the level crossing near Milton and the A14 crossing) that EWR Co state would be required if 4-tracking were required for a northern approach (which we, as detailed above, strongly refute). The other structures requiring modification (Fen Road, river Cam crossing, Newmarket Road and Mill Road) would need to be carried out anyway as a southern approach needs to terminate in Cambridge North station (see point 1 above). But all these works are less than those required for a southern approach.

This discrepancy in construction works between the approaches demonstrates EWR Co’s apparently sanguine approach to risk-based decision making.

3. Reversing Move at Cambridge

EWR Co have made much of the fact that a reversing move (i.e. the driver changing ends of the train) would be needed in Cambridge for onward eastbound traffic.

Two points are worth highlighting here. Firstly, it is not much of a penalty at all. A train approaching Cambridge from a southern approach would need to stop in the station for approximately 3 minutes before proceeding. For a train from a northern approach, the maximum time for the driver to change ends is about 5 minutes – a difference of some 2 minutes!

The second point is that onward eastbound passenger services are excluded from EWR Co’s remit. Although they need take such provision into account (the Sponsor’s Requirements 1.6 state that ‘Consideration should be given to the provision of or integration with services beyond the Oxford Cambridge sections…’), using this weak argument against a northern approach highlights their lack of strong arguments. It is especially rich when, in response to our queries about the problems that a southern approach would cause with freight east of Cambridge, EWR Co claim that it is not within their scope.


  1. The northern approach would not need to be 4-tracked between Milton junction and Cambridge station for the predicted maximum amount of rail traffic including future expansion of services to Wisbech and Norwich. As a result of digital signalling, it could also cater for EWR Co’s aspiration of 6tph. EWR Co have appeared to ignore a grade-separated junction at Milton in their analysis of 4-tracking of this section.
  2. It is not certain whether the southern approach between Hauxton and Shepreth Branch junctions (SBR line) can take any growth in passenger rail traffic beyond EWR’s 4tph until further timetabling work has been carried out by EWR Co. This is because of the severe constraints imposed by Thameslink and other services using the line. It would certainly not be able to provide capacity for the 6tph EWR services stated in the PWOS. This lack of flexibility to provide for growth is contrary to the Sponsor’s Requirements.
  3. If EWR Co’s future assessment of the SBR line shows that they do require to 4-track it, the construction works required is likely to exceed the theoretical additional works required for 4-tracking the northern approach (as stated in conclusion 1, they are not actually required).
  4. EWR Co have not been transparent about the adverse impact of freight using a southern approach on railway operations.


[1] Network Rail Cambridgeshire Corridor Study 2019.
[2] Programme-Wide Output Specification (Technical Report Appendix B 5.20.2) is ‘at least’ European Train Control System (ETCS) Level 2. The current signalling system in the general Cambridge area on existing track (i.e. in addition to the EWR track) is being upgraded to provide a platform ready for digital technologies and is planned to be complete by 2025, five years before the currently planned EWR completion date.
[3] ‘Influence of ETCS on line capacity – generic study’, UIC, Fig 24
[5] By Mvpo666 – Own work, CC BY-SA 4.0,
[6] CBRR Northern Approach Into Cambridge.

15 replies on “Do EWR Cambridge Approaches Need 4-Tracking?”

Thanks for this ongoing interesting analysis. Under a northern approach scenario, and your assertion that 4-tracking of the WAML into Cambridge would be unnecessary, I wonder if a grade-separated junction near Milton would be necessary either? Is it possible that electronic signalling would allow this junction to be at-grade whilst still coping with the traffic demand?
Incidentally, it is interesting to note that one of Network Rail’s main drivers for the decision to build the recent Werrington Dive-under on the East Coast Main Line was to avoid the visual impact of the alternative overbridge and embankments.

It may be possible that a grade separated junction is not required at Milton – this would have to be checked in a more detailed analysis. Although an at-grade junction would reduce construction costs significantly, it would definitely reduce flexibility for additional services.

This is brilliant, thank you. It just highlights the poor consultation process EWR have engaged in so far. All I ask for is an honest and open analysis to arrive at a fair conclusion.
We need to take into account the additional connectivity of the northern route (Northstowe and further East etc), the future economic growth to the north of Cambridge, the (welcome) increase in freight trains and the damage to the landscape of great embankments/cuttings.
There seems to be some ideological obsession with going south that has not be adequately explained.
Please keep up this great work – sciencfitic/factual analysis like this is so powerful – future generations will be very grateful.
Thank you.

Freight – EWR Co have mentioned that there are 44 open access freight paths through Cambridge daily. They have told me that 9 of these are available on the Shepreth Branch Royston (SBR) line (the King’s Cross line) and 35 on WAML. They have said that many of these are not currently used, but have hidden behind the accurate (but unconvincing) argument that actual usage varies on a daily basis and so they can’t give figures. True, but I find it odd that they are reluctant to give some kind of average because for those who live along the existing SBR line, it is highly relevant to know by how much freight traffic could increase. If current usage is (on average) 2 – this is a guess – an increase to 9 is a significant increase.

If freight capacity is increased on earlier stretches of EWR could this put pressure on the current decision not to four track from the proposed Hauxton Junction to Shepreth Junction? I think so.

Cambridge residents may be interested to learn that EWR also told me that “industry systems data..shows 10 [freight open access] paths through Cambridge between 23:00 and 06:00. However not all of these are allocated to freight as some are for engineering trains for maintaining the network”. I have no idea how many of these are used in practice.

Check There were 11 freight trains listed on the Cambridge to Newmarket line in the last 7 days all set to run overnight. But only one of them actually ran and that was last Thursday.

There’s a signficant discrepancy between your tph figures and those from ref [1]. Figure 22 for example, shows a total of 20 tph south of Cambridge (including the 6 tph EWR services and the 1 tph additional KGX service).

My understanding is that where ref [2] says a total of 6 tph for Bedford to Cambridge this includes trains in both directions (this could 3 trains per hour towards Bedford, and 3 trains per hours from Bedford, or 4 trains per hour in one direction, and 2 trains per hour in the other etc.)

Ref [1] also refers to the necessary 4-tracking to support Cambridge South station. This is without any additional services. So clearly, the analysis of whether 4-tracking is required is more complex than simply looking at “open track” capacity.

Section (B) Crossings Movements and Junctions completely omits the necessary crossings required by terminating services. e.g., an incoming Norwich service on the Up Main line would need to cross over to the Down Main line when it returns to Norwich, or crossings required to access available platforms.

(1) The section of track that this post covers is the SBR line between Shepreth Branch Junction and Hauxton Junction (i.e. the Kings Cross line only). The 20tph that are referred to in fig 22 of ref 1 (Network Rail’s Cambridgeshire Corridor Study) are between Shepreth Branch Junction and Cambridge station and includes the Liverpool St line.
(2) Ref 2 (the Project Wide Output Specification) section 5.4 refers to passenger trains in each direction. It ties up with fig 22 of ref 1 which shows all trains in each direction (this shows 6tph or Configuration State 3.5 which I’ve said is unlikely to be realised and couldn’t be accommodated on the SBR line with clock face timetabling but could probably be on the northern approach).
(3) The post doesn’t cover the section between Shepreth Branch junction and Cambridge station so doesn’t argue with their decision to 4-track that section (which includes Cambridge South station). The post emphasises that there are many other issues affecting capacity apart from just the open track capacity. Thameslink services is the main reason why there is a limit on capacity on the SBR line.
(4) The post does mention that one of the benefits of digital signalling is that it allows bi-directional running which alleviates the crossing movements required by terminating trains (i.e. if required, the trains can use the same track that they used for entering a station for a greater length before needing to cross over to the return track). Note that this issue affects a southern approach as well as a northern approach.

Thanks for the correction. The table makes more sense now.

If we consider the 7 tph services to London Liverpool Street and Standsted Airport. These combine with the 6 tph London Kings Cross services at the at-grade Shepreth junction. The line north of Shepreth Junction is 2-track for most of the distance to Cambridge.

Can you explain why the at-grade Shepreth junction and existing two-track WAML has capacity for 14 tph (7 STN/LST, 5 KGX, 2 Thameslink, no freight), whereas the new grade-separated Hauxton junction and 2-track SBR would not have capacity for 13 tph (5 KGX, 2 Thameslink, 6 EWR, no freight at peak time)?

Relaxing the requirement for clockface timetabling for the EWR services at peak times seems a perfectly sensible thing to do, when compared to building substantial new infrastructure.

Can you explain more on why Thameslinks services are such a constraint? There are only 2 tph out of 6 tph on the SBR that are Thameslink services and the Thameslink core is more than 60 minutes away, I would expect this to give some wiggle room in timetabling on the SBR itself. Can you also explain why this constraint prohibitivly affects the EWR services, but allows for the STN/LST services?

A very useful analysis of what I consider to be the major factor determining the cost of the route options. There are 4 trains per hour (each way) on the Cambridge North to Ely line and 6 per hour each way on the SBR . EWR have decided that 4 tracking from Milton will be required which would be expensive because of the River Cam and A14 bridges at Milton. However, at the moment they do not anticipate 4 tracking the SBR though it has more trains and more constraints in terms of scheduling. Could that be because the cost of 4 tracking would be much more on the Southern option because of the M11 crossing, River Cam, Shepreth Junction, Hauxton Rd level crossing, etc. Of course they may revisit the 4 tracking requirement of the SBR once the option decision has been made resulting in a massive increase in cost and disruption. How can we get EWR to carry out a comprehensive capital cost analysis of the Northern and Southern approaches, rather than the ‘qualitative assessment’ before such a major decision is taken?
Keep up the pressure for a proper evaluation of the Northern approach.

The depth of analysis and level of expertise being used here to question EWR competence/intentions is very impressive and reassuring. So please keep going. Living in the Harston/Haslingfield area with the proposed extraordinary structural intentions is frightening, dangerous and expensive. The result will look like an ugly carbuncle on the beautiful face of South Cams. Future generations in this area will never forgive us.

Thanks for this in depth analysis. It is much appreciated.
Let’s hope that EWR Co. are reading it too and that they agree to make a thorough and accurate comparison of the northern and southern approach into Cambridge. Surely they want to find the wisest route too?

One reason I like the northern approach is because between St.Neots and Cambridge the route flows just to the north of the A428 dual carriageway, reducing the impact on the open countryside and villages….and being north of the A428 already, the simplest routing is the northern approach.
I wonder if factoring these aspects into your analysis might strengthen the case for the northern approach?

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