Much has been written about the Crossrail project and the benefits of the Elizabeth line. Nearly everything written about its benefits looks at the benefits to users of the Elizabeth line. But often transport projects have benefits that go beyond direct users. Crossrail is one such project and here we look at the benefits (and the downsides) that this project has bought to users of the Great Western Railway Main Line between Reading and Paddington. In doing so we see how the Great Western Main Line and the train services that use it have been reorganised into a more logical and coherent structure.

Starting with the HST era

It is hard to know when to start this narrative but a suitable place is probably around 1976 with the introduction of the High Speed Train. This revolutionised the Great Western Main Line which, in terms of operating, hardly changed until the recent introduction of the electrified Hitachi Intercity Express Train (IET) in 2017.

The British Rail High Speed Train, often referred to as an Inter-City 125 train, was a great British success borne out of anticipated failure. In the early 1970s all development towards the next generation of trains was geared towards the futuristic tilting Advanced Passenger Train (APT). Originally it was intended that there would be both an all-electric version primarily intended for the West Coast Main Line and a gas-turbine version for non-electrified lines.

For various reasons, including unexpected problems when attempting to introduce tilting trains to the national rail network in Britain, there were considerable doubts about the eventual success of the APT project in some rail engineers’ minds. Taking the opposite approach and relying on tried and tested technology, the mavericks (as they were considered to be at the time) pushed the use of diesel engines to the limit and designed a train that could operate at 125 mph – the same as the APT was reasonably expected to do. This was a big leap forward from the previous British Rail maximum speed of 100 mph. To avoid the need to re-signal the lines involved, the train could stop in the same distance as a conventional 100mph train.

It became clear that the HST would save the day on non-electrified lines that didn’t actually need a tilting train, when the APT was clearly set to be abandoned. But it was equally obvious that the diesel HST would be completely unsuited for the electrified and sinuous West Coast Main Line for which the APT had primarily been designed. In order to fill the gaping hole in the future delivery of trains for routes other than the West Coast Main Line, the HST train was put into production with astonishing speed. This was probably helped by being one of the last of a generation of trains prior to an era when substantial time would be needed for the software debugging of new trains.

HST debuts on the GW main line

Initially, the question appeared to be not where the need for the HST was greatest, but where could it be introduced with the least difficulty and the greatest effect? The answer was obvious. The Great West Main Line was relatively flat and its broad-gauge origin meant that the curves were gentle between Bristol and London. It was also relatively unencumbered by all-stations suburban trains holding the HSTs back from achieving their potential.

Another factor in favour of choosing the Great Western Main line was that there had been a lot of recent signalling modernisation. Just five signal boxes controlled the line between London and Bristol, meaning there was little risk of trains being delayed by either old mechanical signalling or signallers not knowing what trains were approaching their area.

oRIGINAL hst western region power car preserved at the nrm in york

Another great benefit was that parallel with the fast lines (known as the ‘main’ lines) between London and Didcot (a full 53 miles from Paddington) were slow lines (known as the ‘relief’ lines) that could handle other trains, thus enabling the full HST potential to be unencumbered by other rail traffic.

One consequence of this advance in speed was the obvious need to upgrade the main lines to allow for 125mph running. Less obvious, and unheard of in the 1970s, was the need for the ‘slow’ lines to be upgraded to 100mph wherever possible. Diesel multiple units (DMU) in those days could not reach anything like 100mph and the ones on the Western Region were Class 116 DMUs with a maximum speed of 70mph. However, there was a need to run Inter City 100mph loco and coaches sets on the relief lines at times so as not to impede the HSTs on the main lines. It was also the case that if the HSTs had to be diverted to the relief lines, one didn’t want their speed to be nearly halved.

The impact of the HST on the Western Region of British Rail was dramatic. Because of the significant increase in speed now available, it was necessary to ensure all trains on a specific route had been replaced by HSTs before a 125mph timetable could be implemented. Until that happened, HSTs regularly sat at some major stations for ten to fifteen minutes waiting for their timetabled departure, which was based on 100mph timings for that route. The perception of the trains was that they were clean, modern and fast.


The trains were also popular with railway staff as at last the general public had positive comments to make about the railways, in an era when British Rail was the butt of many jokes and frequently criticised in the daily press. Of particular note was the enthusiasm of the drivers. Possibly less so the guards who initially had a noisy guards van at the rear of the engine unit, but this was eventually rectified by partitioning off an area for a replacement guards office in coach ‘A’ and reallocating the former guard’s area to bicycle storage.

As an indication of how drivers received the train, the story goes that ASLEF were pushing for a maximum of three hours driving on HSTs scheduled per half-shift. Swansea depot was due to have drivers retrained for HST work but, in order to comply with ASLEFs requirements, they would have to handover at Reading to drivers based at Reading for the final part of the run from Swansea to Paddington, as at the time the three-hour limit would be exceeded. Swansea drivers were having none of that and wanted to drive all the way to London and were quite happy to negotiate shifts on that basis.

Whilst having HSTs on the Great Western was a boon, it was clear that the restricted allocation meant that full advantage of them could not be made over the entire region. Their existence had to be justified as there was also a pressing need to introduce HSTs on the East Coast Main Line where the commercial benefit of running these trains would be greater.

Over the years to come, things got better for the Western Region of British Rail as more HSTs became available for when the East Coast Main Line was electrified, and the considerable number of HSTs now running entirely ‘under the wires’ became redundant once the replacement electric stock was introduced.

The extra HSTs prompted a change of policy. Previously, HSTs were very much route specific with either the entire service operated by HSTs or none at all. Eventually it was appreciated that this was a needless restriction. In particular the opportunity was taken to fit in the occasional ‘bounce back’ service to and from Oxford by utilising spare off-peak capacity. The commercial benefit of running the occasional HST to Hereford was also realised.

New DMUs

On the DMU side, the first generation DMUs were replaced with Class 165 and 166 Networker turbos from 1991 onwards. Those assigned to Western Region were also known as Thames Turbos. These enabled the withdrawal of not only the previous generation of DMUs but also the elimination of loco-hauled trains as the DMUs were more comfortable than the previous generation – they had toilets and at 90mph their speed and superior acceleration meant that they offered a similar performance to loco-hauled trains. Eliminating loco-hauled trains considerably simplified operation at Paddington and increased the platform capacity as dead time for locomotive movements was eliminated.

Class 166 Networker Turbo DMU

The downside of these improvements was that there was an awkward mix of 125mph HSTs and 90mph diesel multiple units. A typical fast service from Oxford would by operated by a 90mph train, yet would ideally need to use the fast lines between Didcot and Paddington to avoid being slowed down by stopping trains, but in doing so would restrict the number of HSTs that could operate on the fast lines.

HST overstretched

Initially, the HSTs were ideally suited to the Great Western Main Line and the East Coast Main Line. They were designed for long distance, very-limited stop services at 125mph but could also be utilised on 100mph lines with more frequent stops. This fitted in very well with working on the East Coast Main Line. At the time of their introduction, they also fitted in with intended service patterns on the Great Western Main Line. Typical services would leave Paddington and call at Reading then not stop until Bath or Newport (Wales). Some services would also serve Didcot, Swindon, and the embryonic Bristol Parkway station.

As the service became a success, passenger demand from Didcot (by now renamed Didcot Parkway to reflect its additional role), Swindon, and Bristol Parkway grew substantially. Swindon gained an extra platform in 2003 to reflect this and Bristol Parkway eventually went from having two to four platforms.

However, the additional station stops highlighted problems with the engines on the trains. This was not so much a design flaw as usage being other than the designers intended. The engines really were not designed for frequent stops from 125mph followed by rapid acceleration back to 125mph. Apart from increased wear and tear to both engine and brakes, this led to a depletion of coolant. A familiar sight at major HST stations around 30 years ago would have been an HST bowser with a resupply of coolant to avoid the engines overheating. This was to some extent solved by engine replacement with later generation diesel engines better able to handle the frequent changes in speed.

The problem of additional HST stops was exacerbated by the elimination of 100mph loco-hauled trains. This would have left passengers at Maidenhead and Twyford in particular experiencing a substantially diminished quality of service. This would also apply to any passengers on the Henley-on-Thames branch who changed at Twyford or the Marlow branch who changed at Maidenhead. It wasn’t really practical to allow DMUs to run on the main (fast) lines there as this would eat into the number of train paths available. The only practical solution found was to stop some long-distance HSTs at Maidenhead or Twyford.

a busy modern day maidenhead station just after the morning peak

Not only did these outer suburban stops (which is what effectively these had become) prove unsatisfactory because of yet another HST stop, it also meant that passengers were very unlikely to get a seat for their inbound journey on a train that was not designed with standing passengers in mind. However, the service was fast and it did have toilets.

As we shall see, the problem with the service from Twyford and Maidenhead was to get worse before it got better.

Need for 21st century upgrade

By the early years of the 21st century it was becoming obvious improvements were needed. The HSTs were getting on for 40 years old and capacity was becoming an issue with the rise of long-distance commuting. The notion of a train discharging the contents from the toilet onto the track in the 21st century was regarded as unacceptable. The signalling on the line was also due for replacement. It made sense to completely modernise the line with electrification, new electric trains, and new signalling that would be immunised for electrification.

Current day track at Platform 1 paddington – finally faeces free!

Until privatisation, the Western Region of British Rail was perceived as a complete electrification desert. This was not entirely true as Heathrow Express ran an electric service into Paddington from 1998. It seems a little surprising that advantage was not taken to piggyback off this and extend the wires along the relief lines from Airport Junction to the bay platform that then existed at Slough – a distance of less than eight miles. This would have enabled a suburban service from Paddington to Slough and would have been a classic case of ‘electrification by stealth’. By now ‘sectorisation’ had superseded British Rail’s regional structure and Thames Turbo trains had recently been purchased. For whatever reason it seems that either Network SouthEast were not interested or that sectorisation made the issue too complex or that privatisation was already being talked about which would have killed the desire for long term schemes.

Next to come along was the proposal for Crossrail. Originally intended to extend to the west as far as Reading, the proposal as authorised was cut back to Maidenhead. It was a bit of an open secret that the reason for this was the enormous cost of either immunising the existing signalling at Reading or replacing it which, by the rules of the day, would be entirely borne by Crossrail.

With electrification already planned as far as Maidenhead, the case for replacement trains being able to run on electricity seemed unstoppable. As it turned out, the civil servants deciding this chose to recommend to the transport secretary that bi-mode (combined 25kV AC and diesel powered) trains be ordered. The question was then how much electrification?

Given the limited capacity available into London and the ability of electric trains to accelerate much faster, it almost certainly made sense, as an absolute minimum, to electrify from Maidenhead as far as Didcot Parkway and probably as far as Oxford. Didcot Parkway to Oxford is not currently electrified but that is only because it makes sense to do this after Oxford station is reconstructed, which will happen in 2023-2024.

Sidelining Greenford services

Electrification from Airport Junction to Didcot Parkway was an absolute game changer. It meant that diesel passenger trains could be almost eliminated between Didcot Parkway and Paddington. There was just one service that operated throughout the day which would potentially remain a diesel service and this was the suburban service from Paddington to Greenford. However, with the future introduction of Crossrail, it made little sense to start this service from Paddington. It was proposed to reduce this to a shuttle service between Greenford and West Ealing and this necessitated remodelling West Ealing station. Once West Ealing station was remodelled, through services almost ceased to run to Greenford.

One of the rare through trains to and from Greenford is the once-a-day Monday-Saturday GWR early morning train from Paddington to Greenford which calls at Ealing Broadway then West Ealing platform 3 before heading up to Greenford on the branch line. This runs on the relief lines between Paddington and West Ealing before working the day’s shuttle service on the branch line. In order to position the train at Paddington it has previously arrived from Reading, having originated from the traincare depot there, and run in service as a semi-fast train on the relief lines to Paddington.

This contorted diagram has a return evening working. Needless to say, YouTuber Geoff Marshall has travelled at ungodly hours of the day to bring you a video of these little-known workings.

The plan looked complete…

Electrification between Maidenhead and Reading meant that it made sense to extend Crossrail to Reading, now that the lines were already electrified and electrification costs were no longer chargeable to Crossrail.

It seemed that plans looked settled. GWR would have exclusive use of the fast (main) lines, with the exception of 4tph Heathrow Express between Paddington and Airport Junction. The relief lines would be shared by Crossrail, GWR suburban and outer suburban services, and freight.

It seemed like almost everyone was a winner. There were some complaints about the lack of toilets on the Crossrail trains and the unsuitability of the seating for longer commutes on Crossrail. But these were seen as minor issues by the service providers because there would be the alternative of the comfortable semi-fast GWR trains from Didcot Parkway into Paddington.

What was not entirely clear was what would happen to the few peak period direct services between Bourne End and Paddington (Marlow branch) and also between Henley-on-Thames and Paddington. The original plan was for these branches to be electrified but the cost of electrification meant that this was officially ‘paused’ until the price could be brought down. As there was no suggestion at the time that these services would be removed, it appeared that they would continue to be operated by DMUs. So not better off but not worse off.

…but change came

Things then took a surprising turn in March 2017 when the agenda for Programmes and Investment Committee contained a proposal to enhance Crossrail services between Reading and Paddington by taking over some (unspecified) GWR services on the relief lines. The proposal clearly had the approval of the DfT and acquiescence of GWR. Not surprisingly, those complaining about seating and lack of toilets on trains now had an argument of far greater merit.

The proposal didn’t spell out which GWR services were to be removed, but it seemed that they could only be the morning direct services from Bourne End and Henley, and their corresponding evening workings.

In fact, for GWR customers using these direct trains, the consequences were even worse than originally understood. The proposals were approved and extra Crossrail trains were added to the original order. The changes were introduced and today (pre-May 2023 timetable change) the GWR ‘semi-fast’ services between Didcot Parkway and Paddington run almost to the same timings as Crossrail trains, despite calling at far fewer stations between Reading and Ealing Broadway. So not only had some GWR passengers lost out on direct trains, the overall journey to London would be slower despite electrification.

Looking at the issue as a whole it made sense to utilise Crossrail so as to provide greater benefit overall. It also transferred services to TfL that would generate significant extra revenue, whilst not being costly to run. No doubt there was an agreement to compensate GWR train operating company in some way for this. However, following the Covid revenue collapse, the company is being contractually paid for the service specified by the DfT for the service it provides with the DfT effectively pocketing the income from fares..

GWR to concentrate on long distance services

It could be argued that a further benefit of GWR losing some services that would have run on the relief lines is that in London they can concentrate on their core offering – fast trains to the Wales and the West Country. That does leave four self-contained branch line services (treating West Ealing – Greenford as a branch line) operated by GWR joining the Great Western Main Line between London and Reading, which sit slightly uncomfortably in GWR’s remit.

The West Ealing – Greenford shuttle is a bit unusual as it does not connect with any other GWR services. It might make sense operationally for GWR to run this branch, but no train operating company is an obvious fit for running these services. From a passenger perspective, it seems a bit of an anomaly – especially as, unlike the other branches, it lies entirely within the Greater London boundary.

Good News from May 2023

Returning to the development of services on the relief lines, the really good news in this saga is that from May 2023 the half-hourly GWR outbound service from Paddington to Didcot Parkway will run on the main lines between Dolphin Junction (just to the east of Slough) and Paddington. This may seem like a small change, but it really is quite dramatic with both immediate and potential long-term benefits – assuming that this is permanent.

In the other direction (towards Paddington) the workings aren’t quite as good as the semi-fast service remains on the relief lines as far as Stockley Bridge Junction but, crucially, they switch to the main line just before trains from Heathrow join the relief lines. This is slightly less critical as there is an up freight loop between Iver station and West Drayton station.

The inbound GWR semi-fast service from May 2023 will call at all stations between Didcot Parkway and Maidenhead then Slough, and then non-stop to London Paddington with a corresponding journey in the other direction.

The first obvious benefit is that passengers from Maidenhead and Twyford finally get a regular fast service to and from London with an expectation of a comfortable seat and a toilet available. Journey times will be an impressive 32-36 minutes from Twyford and 24-29 minutes from Maidenhead. Passengers from stations between Didcot Parkway and Reading (exclusive) will have very little incentive to change train at Reading and will benefit from a faster direct service between their station and London.

Less obviously, most passengers on trains to and from Oxford will benefit from their trains not calling at Slough, as non-stop London services from Slough are now catered for by the GWR semi-fast service. The downside of this for passengers joining at Slough is that the GWR semi-fast will actually take between two and four minutes longer from Slough to London than the current Oxford service. This can be explained because the May 2023 service will be a 110mph electric train instead of a 125mph bi-mode train running in electric mode. A further potential cause of extra running time is the ‘weave time’ needed to traverse the points between the relief and main lines at Stockley Bridge Junction. An upside, arguably, for Slough passengers from May, is that all London-bound trains will leave from the same platform at Slough. Minor downsides are that passengers from London to Windsor & Eton Central will lose their cross-platform connection at Slough and passengers from London wishing to leave the station by the main exit will, from May, have to use the footbridge to do so.

A consequence of the reorganisation of services in the May 2023 timetable is that it does appear that all services from platforms 1-5, 8, and 9 at Paddington will have a first stop at Reading. This could be an opportunity to reconfigure the ticket gates at the gated platforms (2-5) so that only passengers with tickets valid as far as Reading are admitted, if this is not already the case. It is certainly the situation now that Freedom Passes, 60+ passes, and zone 1-6 Travelcards are already rejected at the ticket gates serving platforms 2-5.


Perhaps more importantly, a potential future benefit of the GWR running on the main lines from Paddington to Dolphin Junction is that the relief lines east of Dolphin Junction will become the preserve of only the Elizabeth line and freight trains, which should lead to increased flexibility and opportunity.

Freight trains have scarcely had a mention so far in this article yet they may be the key to future Crossrail improvements. Freight services are important along this line. They tend to convey traffic unsuitable for transport by road such as aggregate from Merehead Rail Depot (serving Torr Works Quarry in the West Country) to Acton Yard. They can also be quite a constraint on what passenger services can be run, as a loaded aggregate train is typically limited to around 40mph. There is a freight relief loop between Iver and West Drayton in the ‘up’ direction (towards London) which does mitigate things slightly.

The main problem with planning passenger services around freight trains is the timetable regime in place which leads to an awful lot of allocated freight paths on which services ‘run as required’. These are known as Q paths.

Naturally, freight operating companies make sure they run the occasional train so as not to lose their right to a slot. In the main, these slots are not used on a regular daily basis. If the number of slots were reduced and not assigned to one freight company but instead required freight operating companies having to reserve in advance when they actually needed them, more passenger trains could be run. Similarly, if the few Q paths in peak hours were eliminated then more passenger trains could be run in peak hours.

Future Opportunities

It follows that with changes to the freight regime there would be opportunities for an increase in capacity for Elizabeth line trains east of Dolphin Junction though in practice we are talking about between West Drayton and Paddington and Heathrow and Paddington. The latter assumes spare capacity in the Heathrow tunnels and specifically to Terminal 5 because there is no spare capacity on the single line between Terminals 2&3 and Terminal 4.

There are other opportunities to improve capacity such as electrification of freight trains and improved signalling. The GWR line between Paddington and Airport Junction is planned to be enhanced to ETCS (European Train Control System) as being currently implemented on the East Coast Main Line. But when that will happen is unknown. Another possibility is that Network Rail allows closer timetabled spacing of services.
At present it appears that Elizabeth line services cannot be less than 3½ minutes apart. Part of this limitation is probably caused by the one-minute dwell time needed at Ealing Broadway and other places. Eventually the off-peak service on the Elizabeth line is expected to be at 3 minute intervals between Paddington and Whitechapel. It would therefore be helpful if off-peak minimum intervals west of Paddington were also not more than 3 minutes.

The Main (Fast) Lines

On the main line, trains can depart from Paddington as close as two minutes apart. However, probably due to signalling constraints when leaving Paddington and negotiating the pointwork outside the station, it does not follow that this can apply to all departures.

It does seem that the main lines in and out of Paddington are almost at capacity and generally running 16tph throughout the day. This consists of 10 non-stop trains to Reading, two semi-fast trains to Didcot Parkway, and four Heathrow Express trains per hour. Nearly all non-stop services to Reading are by I25mph IETs, but the service to Newbury is generally operated by 110mph Class 387 electric multiple units.

It is believed that this is near the practical limit to capacity, with Modern Railways (April 2023) claiming that running the Didcot semi-fast services on the main lines was only possible because plans for a ‘superfast’ service to Bristol have been dropped. This was a consequence of the downturn of traffic since the pandemic. Strictly speaking, there is little downturn of long-distance traffic on the Great Western, but it could have reasonably been expected to have considerably increased by now with the newer trains had it not been for the pandemic.

On the relief lines, it appears that capacity is being artificially constrained by the number of freight paths allocated but rarely used. Given the unsatisfactory usage of Elizabeth line trains serving Heathrow to provide the only service to Acton Main Line and Hanwell stations, and the desire to run extra Elizabeth line trains to Heathrow Terminal 5, extra capacity on the relief lines could be beneficially used.

Of course, planning for something that in future allows more peak services to run on the Elizabeth line is impossible, unless you have the rolling stock for it but, as mentioned in The Slow Death of Heathrow Express article, there are some possible ways of getting around this should that be necessary.

Overall a great improvement

Timetable-wise, the Great Western Main Line has developed from something that was a bit of a mess to something that is getting close to perfection with electrification and better separation of services. If one could criticise, an outstanding issue is that GWR departures from Paddington National Rail station aren’t all quite clockface regularity, with a slight ‘wobble’ in timings. This is probably down to the multiple platforms at Paddington and the varied timings for routes in and out of them. At present there are probably not enough platforms for services to the various different destinations to consistently arrive and depart from the same numbered platform, which would probably be a prerequisite to a perfect repeating timetable with trains departing at exactly the same times past the hour on all routes with an hourly service or better.

It seems that, although it took a long time to reach the service to be achieved by the May 2023 timetable, there are no losers compared to the service in HST days, unless you consider the loss of a direct DMU from a couple of the branches to outweigh the opportunities for a faster, more pleasant service with a single change of train. Ultimately, Crossrail has benefitted not only Elizabeth line services, but also those GWR passengers whose service has improved as a consequence of the Crossrail enhancements.

Thanks again to Matt for proof-reading.

The post The Great Western Main Line to Reading in the era of Crossrail appeared first on London Reconnections.

Generated by Feedzy