Guy Fawkes’ Day, 5 November 2010, and the 15:05 South West Trains service left Guildford for Waterloo. It was an eight-car train, made up of two Class 455 electric multiple units coupled together. Twenty minutes later, it was departing Oxshott station.

At the same time, a DAF 75 ready-mix concrete lorry was travelling south on the A244, from a concrete batching plant at Byfleet to a construction site at Epsom. At the wheel was a driver with only three weeks experience, in his first week as an unaccompanied driver following a period of training. With 14 tonnes of concrete on board, the vehicle weighed a total of 25.6 tonnes.

Over the edge

The A244 crosses the railway close to Oxshott station. It approaches the bridge (Bridge 11) at a slight left-hand angle. As the lorry came up to the bridge, its front left wheel made contact with the end of the bridge parapet which was obscured by vegetation. The impact was severe enough to break one of the wheels studs. Following through, the rear of the lorry also hit the parapet end.

Image2 [online]

Photo: RAIB.

After travelling a little further down the bridge, the lorry hit the left hand brick-built parapet, demolishing 14.3 metres of it which fell onto the railway below. Most of it fell harmlessly onto the side of the cutting, but some masonry landed on coach five of the train that was coincidentally passing under the bridge at the time. There was a loud bang heard inside the train and luggage was thrown off the overhead racks. However, there were no injuries caused to the train’s guard and the fourteen passengers who were in the carriage at the time.

However, a few seconds later the lorry, dragged off the bridge after its left hand wheels had demolished the parapet, landed on the front left-hand corner of coach six. The force of the impact crushed the roof downwards, detaching the cantrail from the corner post. The angle this created rolled the lorry off onto the left hand cutting face alongside the train.

The brakes on the train came on automatically, possibly due to damage to a brake supply wire. As the train slowed down over the next 14 seconds the lorry scraped along the side of the train, breaking up. Coach seven was damaged, but a large section of the wreckage made a heavy impact on the forward door of coach eight, stoving it in badly. This knocked the whole carriage sideways, deflecting the track 350mm to the right and derailing the rear bogie although the whole train remained upright. The conductor rail was also pushed out of place.

The aftermath

There were ten passengers travelling in coach six. One was badly injured and trapped by the collapsed roof while five others were less badly hurt. Fortunately, there were no passengers in coach eight.

Once the train had stopped, the driver informed the local signaller who blocked the line, turned off the power and informed emergency services. The guard, using a ladder from the cab, got all the passengers off the train with the exception of the badly injured one who was trapped. An off-duty police officer who had been travelling on the train stayed behind to comfort that passenger until paramedics arrived 18 minutes later.

The lorry driver had also been trapped in his cab, but he was safely removed to hospital where he remained for two days.

The result of this accident was a badly damaged Class 455. All four carriages were in need of repair, so the whole unit was shipped off to Railcare in Wolverton near Milton Keynes for an engineering assessment.

Anyone got a bodyshell?

The general condition of the train was good, it had only returned from heavy overhaul one month earlier. Being a steel bodied train, its coaches are derived from British Rail’s successful Mark 3 design, the engineers at Railcare were able to repair three of the cars by conventional means. The rear coach needed a lot of work, the roof and side had been extensively damaged and the door needed to be completely replaced, but it was at least repairable.

The coach that was struck by the lorry, however, was in far worse condition. The weld that joined the cantrail to the front corner post had failed. This stopped the post supporting the roof and absorbing the energy of the impact, which is why the whole roof had come down over the first ten seats. Structural engineers from Railcare and consultants Atkins discovered that there was a significant diagonal twist to the whole structure. The coach was therefore basically scrap.

Unsurprisingly, Class 455 bodyClass 455 donor vehicle [online]shells are in short supply. Fortunately, Railcare knew of a Class 210 coach that was in storage belonging to Eversholt Rail. Class 210 was a prototype class of diesel multiple unit which was built in the 1970s but withdrawn in the 1980s. Only seven coaches had been built, and most of those were scrapped. However, one was located and,
like the Class 455, it was a Mark 3-derived unit.

The Class 210 coach was obtained and shipped to Wolverton for inspection. On arrival, Railcare engineers went over it in detail both to establish its condition and how it differed from the Class 455 coach it would become.

Spot the difference

The most obvious difference was that the 210 was a DMS (driving motor standard) so it had a driver’s cab at one end. That would have to go but, fortunately, one intermediate end on the 455 MSO (motor standard open) could be reused.

The other differences were more subtle, but potentially equally problematic. For example, the entire headstock assembly, including the dragbox, would need to be changed. The dragbox of the Class 455 is shallower in the area above the traction motor when compared with the Class 210 and it was not practicable to modify the existing Class 210 dragbox to gain the necessary clearance required.

The most significant difference from the perspective of structural strength was the thickness of the material used for the vehicle solebars; 6mm as compared with 8mm of the Class 455 MSO. Also, while the basic underframe arrangement of the Class 210 and Class 455 is very similar, some differences do exist. The Class 455 uses, almost exclusively, cross members made from 6mm thick steel compared with 5mm thick on the Class 210.

As a result of these and other differences, the Railcare engineering team, supported by Atkins, set about developing proposals for the conversion. Before being implemented, these were checked using a finite element analysis (FEA) model which was specially developed
to ascertain whether the discrepancies could remain or further stiffening would be needed. Atkins was able to confirm that the main structure could remain as-built, although some cross members would need to be replaced.

Brackets, bolsters and bogies

So far as the mechanical side was concerned, there were a number of brackets and other structures needed to support the traction control equipment. The distance between the centres of the air bags also differs between the two vehicles (50mm) and for this reason it was necessary to replace the bolster assembly resulting in two new bolster sub-assemblies being manufactured.

To remove and replace the bolsters on the Class 210 introduced further risks to the task of converting the vehicle; the alignment of the bolsters is critical to achieving the correct cross-axle wheel load tolerance and the vehicle’s swept envelope could have been upset.

Externally, the old ventilation equipment was removed from the Class 210 bodyshell, new carlines and 3 new roof mounted ventilator cowls added and the roof skin modified to make this area the same as a Class 455. Some local modification to the roof skin was required and the interface plate welded into position. The Class 455 has a gutter running the length of the vehicle, just above the orange coloured overhead cable warning line. This feature is not present on the Class 210 and had to be added.Class 455 [online]

Both motor bogies on the Class 455 MSO had suffered significant damage and the bogie frame side wall has been dented.

One of the override beams has been bent along with distortion of the lateral damper and both traction links and brackets. The bogies were removed and the damage to the frames repaired by the engineering team at Wolverton. Then, to maintain the existing warranty, they were sent to Unipart Rail for C4 overhaul.

After the interior had been refitted, largely taken from the original Class 455 with some new parts, the body was completely repainted and it was difficult to tell it actually came from a different train.

In March 2013, over two years after the accident, train 455913 was ready to re-enter service. It had been a complex task as Phil Mitchell, projects and engineering director for Railcare, explained: “The challenges of taking one kind of vehicle and making it into another are significant. Not only are you undertaking a significant repair but ensuring that all aspects of the newly built vehicle comply with the design and build specification of the Class 455. We are really pleased with the outcome of this complex project and look forward to supporting the test phase and seeing the train back in passenger service.”

The train is now undergoing final sign off before traction tests and trial running. It is expected to be back carrying passengers shortly.