AI Test – Roll out of rail rolling stock in the UK?

AI, rail, South Wales Metro 14 Minutes

Given the news today re TfW’s tram-trains and their protracted/delayed roll-out, I thought I’d ask Claude to review all the issues affecting rolling stock roll-out in the UK over recent years.

I did this very quickly – 10 minutes – so cant vouch for the fine details. But clearly problems and delays in rolling stock implementation is a common feature of UK railways.

This is what I asked Claude…

Can you review the introduction of new rail rolling stock in the UK and for each type, summarise the issues rail operators faced and addressed in completing their introduction to service

This is the answer I received after a few minutes……(those more expert and knowledgeable please review and check)

New Rolling Stock in the UK: Introduction Issues and How They Were Addressed

Nov 5, 2026 · @Mark

Nearly every major UK fleet introduced since 2016 entered service late, often by years. The same five causes recur: train software (especially TCMS), integration with legacy signalling and train protection, cab design that drivers’ unions would not accept, driver training capacity, and defects found only once trains were in traffic.

This review covers passenger fleets introduced c.2016–2026. Dates are first passenger service unless stated.

FleetBuilderOperatorPlanned entryActual entryMain issues
Class 800/801/802 (IET)HitachiGWR, LNER, TPE, Hull Trains—Oct 2017Bodyshell fatigue and stress-corrosion cracks; fleet-wide withdrawal May 2021
Class 385HitachiScotRailSep 2017Jul 2018Curved windscreen doubled signal reflections; late electrification
Class 805/807 (Evero)HitachiAvanti West Coast2023Jun 2024 / Nov 2024Static-test issues, training
Class 810 (Aurora)HitachiEast Midlands Railway2023Dec 2025Late delivery; poor early reliability forced a reduced timetable in Jul 2026
Class 345Bombardier/AlstomElizabeth line2017–20182017; Heathrow Jul 2020ETCS and legacy ATP integration; software; 84 ETCS non-conformances
Class 710BombardierLondon OvergroundMar 2018May 2019TCMS software (34+ versions); multiple working approval
Class 720Bombardier/AlstomGreater Anglia, c2cMar 20192020TCMS software, knock-on from 345/710
Class 701 (Arterio)Bombardier/AlstomSouth Western Railwaymid-2019Jan 2024Software, cab design, union disputes, driver training; 45 of 90 in service May 2026
Class 730Bombardier/AlstomWest Midlands Trains2020–21Nov 2023; 730/2 Jun 2025Software, pandemic; 730/2 cab noise above 90mph
Class 700SiemensGovia Thameslink—2016On-board software; early unreliability; May 2018 timetable
Class 755/745StadlerGreater Anglia—2019Track circuit detection failures; level crossing near miss
Class 777StadlerMerseyrail2020Jan 2023Pandemic, guard dispute, software faults
Class 555StadlerTyne and Wear Metro2024Dec 2024Low-adhesion traction, door dispatch fault (fleet paused), air-con leaks
Class 195/331CAFNorthernOct 2018Jul 2019Gangway/coupling contact on tight curves; late deliveries; yaw damper defect
Nova 3 (Class 68 + Mk5A)Stadler/CAFTransPennine Express—2019Reliability, cracks, stabling noise, training; withdrawn Dec 2023
Class 769 (Flex)Porterbrook/Brush conversionNorthern, TfW, GWR2019TfW 2020; Northern 2021; GWR noneMode-switching reliability, gauging, union acceptance
Class 197/231/756/398CAF, StadlerTransport for Wales—2023–2026Manufacturing and infrastructure delays; Class 398 software, fleet withdrawn Sep 2026

Hitachi Class 800/801/802 (IET)

The IETs entered service broadly on time with GWR in October 2017. The big test came later, on 8 May 2021, when the whole Class 80X fleet at LNER, GWR, TPE and Hull Trains was withdrawn for inspection.

Issues

  • Fatigue cracks at the yaw damper bracket and anti-roll bar fixings on the bolster, first found at North Pole depot in April 2021. Eight GWR trains were withdrawn and a National Incident Report issued.
  • On 7 May 2021, separate cracks were found near the lifting (jacking) plate welds at the other end of the bolster. That triggered the fleet-wide withdrawal.
  • Similar cracking was later found on Hitachi Class 385 and 395 units. These were not withdrawn because their design differs and the risk was judged low.

How it was addressed

  • Every vehicle was inspected, and a safety case was built for running trains with known cracks under a monitoring regime. Lifting-plate-crack trains returned from 14 May 2021 and yaw-damper-crack trains from 12 June 2021.
  • Operators borrowed stand-in stock, for example c2c and GTR Class 387s on GWR diagrams.
  • Hitachi agreed a fleet-wide permanent repair and modification programme. ORR published a lessons-learnt review in April 2022 covering how the industry found, assessed and recovered from the defect.
  • Knock-on effect: the follow-on AT300 orders for Avanti (805/807) slipped.

Hitachi Class 385 (ScotRail)

The 70-unit fleet for Edinburgh–Glasgow electrification was due in September 2017. It entered service in July 2018, about ten months late.

Issues

  • Late electrification of the route, and late construction and delivery, held back driver training.
  • In February 2018, during night test runs, drivers found the curved laminated windscreen created double reflections of signal aspects. ASLEF said it would refuse to work the trains until this was fixed.

How it was addressed

  • Two windscreen designs were trialled on one unit with drivers. A flatter screen was adopted, which needed the cab bulkhead moved back. Retrofits were done at Knorr-Bremse Springburn.
  • Scottish ministers said the taxpayer would not pay for the modifications. Penalties were left for ScotRail and Hitachi to settle.
  • ScotRail leased 10 Class 365s from Eversholt as a stop-gap and ran shortened trains. The interim fleet won an industry award for project management.

Hitachi Class 805/807 (Avanti) and Class 810 (EMR)

The later AT300 derivatives show that a mature platform still takes years to enter service. Both orders were placed in 2019.

Class 805/807 Evero (Avanti West Coast)

  • 13 bi-mode 805s and 10 electric 807s were ordered in December 2019, all due in service by 2023.
  • Entry slipped to 2024 because of issues found in static testing, the knock-on from the 2021 Class 80X cracking, and training.
  • How it was addressed: a phased launch. Six 805s started on the North Wales route on 2 June 2024. The 807 had a soft launch on 26 October 2024 and timetabled Liverpool services from 11 November 2024. The Class 221 Voyagers were retired in December 2024.

Class 810 Aurora (East Midlands Railway)

  • 33 five-car bi-modes were ordered in August 2019 for the Midland Main Line, with testing planned from mid-2022 and service in 2023.
  • ORR authorised the trains in May 2025, but the first passenger run was not until 3 December 2025.
  • In service, reliability fell below expectations. Combined with maintenance problems on the Class 222 Meridians it replaces, this led EMR to bring in a temporary reduced intercity timetable from 20 July 2026.
  • How it is being addressed: Hitachi is putting in reliability improvements during the entry-into-service phase. EMR has moved to a controlled roll-out through 2026 and 2027, rather than its original cascade plan.

Aventra Class 345 (Elizabeth line)

The Class 345 entered service in 2017 on Liverpool Street–Shenfield, but working it through every signalling system on the route took years. Its software was an evolution of the Class 378 Electrostar TCMS, not the new Aventra software family. Its problems were mainly about integration.

Issues

  • On the Heathrow branch, the train had to work with the legacy Heathrow Express ATP and the ETCS Level 2 overlay. Running to Heathrow was delayed by just over two years, and ETCS testing at Melton slipped as early as 2018.
  • Once the ATP interference was solved, on-board ETCS software caused further problems, including brake applications when the GSM-R link dropped.
  • All nine-car units were withdrawn in mid-June 2020 after a software fault, and were temporarily replaced by seven-car sets.
  • Compatibility work found 84 TSI non-conformances in the ETCS fit. In-service incidents continued after ORR authorised the trains in May 2020.
  • Software was one of the reasons the central section opening slipped from December 2018.

How it was addressed

  • A staged opening strategy, with legacy Class 360s and 315s kept as fallback while the 345 took over each route in turn. Heathrow service by 345s started on 30 July 2020.
  • Repeated software drops, ending in the ELR100 train and signalling release before Trial Operations.
  • ORR authorisation came with a condition to close the non-conformances by 31 March 2024. ORR also required MTR to do a root-and-branch review of software specification. MTR and RfL jointly commissioned an independent audit and software-integrity workstreams.

Aventra Class 710 (London Overground)

The 710 was the first Aventra to use the new software family, and it hit the problems that later delayed every Aventra after it. TfL ordered the fleet in 2015. It was due on Gospel Oak–Barking from March 2018 but carried passengers only on 23 May 2019, fourteen months late.

Issues

  • The Train Control and Management System (TCMS), which manages safety-critical functions such as braking, would not run reliably. The first 710/2s used the 34th version of the software.
  • Multiple-unit working for the West Anglia 710/1s needed more than 40 software versions before it was approved, delaying them by over a year.
  • TfL had let the Class 172 diesel leases expire on the newly electrified GOBLIN. The route was left with three borrowed Class 378s and a skeleton service.
  • Drivers trained on earlier software needed extra training days after each new software drop.

How it was addressed

  • Bombardier ran iterative software releases. The first units went out in a small, phased way: two in traffic and one spare.
  • The Deputy Mayor put pressure on Bombardier directly.
  • Approval of multiple working in early 2020 was seen as the breakthrough that unlocked the 720 and 701 programmes.

Aventra Class 720 (Greater Anglia)

Greater Anglia’s 111-unit order (89 five-car and 22 ten-car) was due to enter traffic from March 2019, but did not run before 2020.

Issues

  • Bombardier’s production and test resources were tied up with the late 345 and 710 programmes.
  • The 720s also had their own TCMS faults affecting safety-critical systems, including braking.

How it was addressed

  • New TCMS software versions were installed and tested from September 2019, followed by a phased roll-out once multiple-working approval had been won on the 710.
  • Greater Anglia kept older fleets in traffic and relied on its Stadler 745/755 fleet to carry the wider renewal.

Aventra Class 701 Arterio (South Western Railway)

The 701 is probably the most delayed new-train introduction in UK history. Ordered in 2017 and due from mid-2019, with the whole fleet in service by the end of 2021, the first train carried passengers only on 9 January 2024. By March 2025, only five of the 90 trains were in service.

Issues

  • Software faults common to all Aventras, plus 701-specific defects in door obstacle detection and the coupling process.
  • Concerns from drivers’ unions about the cab design, and a long dispute over working practices. SWR accepted the first units in late 2022 but could not start driver training.
  • Network Rail’s caution over route acceptance.
  • Once the software was stable, the limiting factor became training enough drivers. Dozens of finished trains sat in storage at Long Marston and elsewhere.

How it was addressed

  • Software upgrades and provisional acceptance of batches, followed by a phased launch on a few routes at a time.
  • After SWR moved into public ownership on 25 May 2025, the new managing director was tasked with an accelerated introduction plan. The number of units in traffic rose from about 12 in mid-2025 to 45 by May 2026.
  • The target is all 90 units in service by early 2027, releasing the Class 455 and 458/5 fleets.

Aventra Class 730 (West Midlands Trains)

WMT’s 84-unit order (48 three-car 730/0s and 36 five-car 730/1s and 730/2s) was the fourth Aventra fleet in a row to run about two years late. The 730/0 entered service on 13 November 2023 and the 110mph 730/2 on 9 June 2025.

Issues

  • Shared Aventra software maturity problems. WMT also cited the pandemic.
  • The 730/2 is the first Aventra built for 110mph, and above 90mph its cab was too noisy.
  • Late delivery stalled the planned cascades, including Class 323s to Northern and Class 170s to EMR.

How it was addressed

  • ORR authorised the 730/0s in February 2022, followed by a staged deployment.
  • The 730/0s were used temporarily on London Northwestern’s WCML services out of Euston to allow the Class 319s to be withdrawn. They moved to the West Midlands (Wolverhampton–Walsall from February 2024, then the Cross-City line) once the 730/2s were ready.
  • The 730/2 cab noise was treated before entry into service.

Siemens Class 700 (Thameslink)

The 115 Class 700s were not seriously late, but they were unreliable for roughly their first year, and the wider programme around them failed in May 2018.

Issues

  • Siemens struggled to finalise the on-board software, which delayed GTR’s acceptance of the first train. Early faults were mostly software: screens, smoke detection and AC/DC changeover at Farringdon.
  • The May 2018 timetable that relied on the new fleet collapsed, mainly because of late timetable planning and too few trained crews. ORR later fined GTR £5 million over passenger information.

How it was addressed

  • Software fixes over 2017. GTR’s engineering director said in late 2017 that most problems had been solved.
  • Earlier, DfT had approved a more gradual service build-up, with the final Thameslink service increase deferred to December 2019.

Stadler Class 755/745 (Greater Anglia)

The Stadler FLIRTs arrived broadly on schedule in 2019. Within months, though, they showed a train–infrastructure interface problem that cut rural services in December 2019.

Issues

  • On 5 December 2019, a Class 755 reached Norwich without being detected by track circuits from Trowse swing bridge. Further track circuit operation incidents followed.
  • At one level crossing, the barriers rose as a 755 approached, and the train came within about a quarter of a second of hitting a car.
  • Suspected causes were the wheel–rail interface (including flange lubrication), autumn railhead contamination and the signalling equipment itself.

How it was addressed

  • At Network Rail’s request, Greater Anglia cut the number of branch-line trains while Network Rail led an investigation with Stadler and GA.
  • The three areas investigated were track and signalling, autumn conditions, and the wheel/track interface. Driver training and further roll-out paused while it ran.
  • Detection reliability was restored before full roll-out resumed in early 2020. The risk to the related Class 745 EMU programme was then cleared.

Stadler Class 777 (Merseyrail)

The 777s replaced the 1978–80 Class 507/508 fleet. Planned to start in 2020, the first entered service on 23 January 2023. Merseytravel bought the trains directly, not through a ROSCO.

Issues

  • The pandemic disrupted manufacturing, testing and European supply chains. Flooding at the factory also delayed the first sets of doors.
  • The trains were designed for operation without guards. The plan to move guards into other roles led to a long dispute with the RMT.
  • After launch, software faults led at one point to the whole fleet being withdrawn temporarily. There were further sliding-step and door faults, and problems on the new Headbolt Lane extension.

How it was addressed

  • A negotiated agreement with the RMT on onboard staffing.
  • Phased route-by-route introduction, starting on the Kirkby line. Line closures were used for enabling works, and older 507/508s were kept as a fallback.
  • Software fixes with Stadler. The Metro Mayor raised the poor performance with Stadler directly, and performance improved through the summer of 2023.

Stadler Class 555 (Tyne and Wear Metro)

Nexus’s £362 million, 46-train fleet had its first passenger run on 18 December 2024. Completion is not expected before 2027.

Issues

  • Testing in early 2024 showed traction problems when railhead conditions were poor.
  • In April 2025, all nine units then in service were withdrawn after a door dispatch fault was found. The 1978 Metrocars covered the whole service again.
  • From summer 2025, water from the air-conditioning leaked into saloons in hot weather, taking units out of use. Clearance to run on the Network Rail-owned Sunderland line came later still.
  • By January 2025, only about 25 of around 200 drivers had been trained. Meanwhile the old fleet was shrinking: 69 of 90 Metrocars were left in service at the start of 2025.

How it was addressed

  • A deliberately cautious phased introduction, starting with a single weekday diagram, so that faults could be contained.
  • Lessons from trial running were built into later units at the factory, so they arrived ready to run.
  • After the door dispatch issue was fixed, roll-out resumed in May 2025, aiming for 23 sets in service by the end of 2025. Stadler is still investigating a permanent fix for the air-conditioning leaks.

CAF Class 195/331 (Northern) and Nova 3 Mk5A + Class 68 (TPE)

Both were franchise-committed fleets for the North. The CAF multiple units are now established. The loco-hauled Nova 3 sets were withdrawn after four years.

Class 195 (DMU) and Class 331 (EMU), Northern

  • CAF was contracted to have the 101 units in service by October 2018. The first nine entered service on 1 July 2019.
  • Testing was suspended in early 2019 because inter-car couplings touched the bodies on tight curves. There were also smaller cab faults: driver’s door, wipers and AWS volume.
  • Assembly at CAF’s new Newport plant ran late, so up to 23 Pacers were kept until May 2020.
  • In 2021, a yaw damper arm came away from a 195 at Newton Heath. Some 24 units were withdrawn for checks.
  • How it was addressed: coupling geometry was modified before service. The Pacers were kept on lease. Shock absorber brackets were inspected and repaired across the fleet.

Nova 3 (DRS Class 68 + CAF Mk5A push-pull), TransPennine Express

  • Introduced in 2019, after Nova 1 (802) and Nova 2 (397), which TPE prioritised.
  • The push-pull software linking the loco to the Mk5A driving trailer was hard to get right and stayed fragile. There were electrical failures, and cracks found on two sets in 2023 meant daily safety checks.
  • Residents in York and Scarborough complained about noise and fumes from idling and stabling. Too few drivers were trained on the sets.
  • How it was addressed: TPE first removed Nova 3 from Liverpool–Cleethorpes, then withdrew the fleet entirely in December 2023, keeping 22 Class 185s instead. The Mk5As were later lined up for Chiltern.

Class 769 Flex conversions and the Transport for Wales fleets

Class 769 Flex (Northern, TfW, GWR)

  • Porterbrook and Brush converted surplus Class 319 EMUs into bi-mode (and, for GWR, tri-mode) units, adding diesel alternators. The aim was to fill gaps left when electrification schemes were cut. Northern hoped to use them from 2019.
  • Development had “numerous delays and reliability problems”, especially around switching between power modes. Exhaust stacks had to be modified for gauge clearance before main-line testing.
  • TfW put the first unit into traffic in 2020, and Northern followed in 2021. GWR’s 769s, the most complex tri-mode version, were never accepted by the unions or used with trained drivers, and went off lease in March 2023.
  • How it was addressed: Northern removed the third-rail equipment to simplify its units and used them in bi-mode only. TfW did extra work to keep its units running, but they were later withdrawn as new fleets arrived.

Transport for Wales (Class 197, 231, 756, 398)

  • TfW deliberately phased its £800m new-fleet programme: CAF Class 197 from January 2023, Stadler Class 231 from March 2023, tri-mode Class 756 from winter 2024.
  • The programme was delayed by manufacturing issues and late Core Valley Lines electrification. Training crews on several new types at once also slowed it, and the earlier Vivarail Class 230 suffered thermal incidents before its builder went into administration.
  • Stadler Class 398 Citylink tram-trains: 36 delivered from March 2023, but first passenger service only on 23 June 2026. They were withdrawn on 19 September 2026 after repeated failures, while Stadler works on software updates.
  • How it is being addressed: 756s and 231s cover the routes meant for the 398s. Fleets have been reshuffled, and the 398s will return only after further validation and testing.

Cross-cutting lessons

Operators who got through introduction successfully did the same few things: phased roll-out with a fallback fleet, early driver involvement, and contracts that kept old stock until the new fleet proved reliable.

Recurring issueFleets affectedWhat worked
Immature TCMS / on-board software345, 710, 720, 701, 730, 700, 777, 398Iterative software drops; small first batches; one TCMS baseline across follow-on orders
Train–signalling integration (ATP, ETCS, track circuits)345, 755, 555Staged opening by signalling area; joint Network Rail–builder–operator investigations; early interface testing
Cab ergonomics and union acceptance385, 701, 777, 769 (GWR)Drivers testing mock-ups and prototype screens early; agreeing staffing before delivery
Driver training capacity701, 555, 710, TfW, 810Training started before acceptance; extra trainers; avoiding retraining after each software drop
Defects found in service (structural, HVAC, doors)80X, 195/331, 555, Nova 3Fleet-wide inspections plus a monitored return-to-service case; fixes built into units still at the factory
Old leases ending before the new fleet is ready710 (GOBLIN), 385, 555Lease extensions or stop-gap fleets (365s in Scotland, 387s on GWR)

A short whole-fleet pause, as Nexus, Merseyrail and the IET operators chose, was disruptive. But it meant trains came back with a defined fix or safety case, rather than failing repeatedly in service.

Sources

Open question: 720 and 755 first-service dates come from secondary reporting. Check them against Greater Anglia records before you cite them in print.

Published by @swalesmetroprof

Professor of Practice in Connectivity at Cardiff University's School of Geography and Planning. Conceived & been working on The South Wales Metro since 2010...also KOd some thinking re Swansea Bay Metro and Cardiff Crossrail!

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