Croydon crash
Fourteen months after the tram crash that killed seven passengers, ANDY COWARD looks back at the accident and analyses the safety recommendations made by the Rail Accident Investigation Branch
Fourteen months after the crash that killed seven passengers, RAIL analyses the recommendations to ensure tram safety.
On November 9 2016, as the world woke to the news that Donald Trump had won the race to become the 45th President of the United States, an early morning London Tramlink tram departed from New Addington, working a service to Wimbledon.
Just over 14 minutes later, as the tram approached Sandilands Junction on the outskirts of Croydon town centre, it derailed on a sharp radius curve, overturning onto its right-hand side. The news pictures which emerged later that morning as daylight broke showed the stricken tram lying on its side, leaving observers questioning what could have gone so badly wrong.
Of the 69 passengers on board the tram that morning, seven were killed. A further 51 people required hospital treatment, with 16 of them classed as having serious or lifethreatening injuries. Only one passenger on board the tram escaped without any physical injury. The driver of the tram also suffered minor injuries in the accident.
Under normal circumstances, it was the sort of major accident that would have dominated the rolling news programmes throughout the day. However, the US election was such a huge news story the tram accident at Sandilands Junction was somewhat overshadowed and became very much a secondary news item in the media, despite the tragic loss of life. Even so, it was still one of the worst rail-related accidents in this country for many years.
Up to that point, the UK tram industry had enjoyed an excellent, almost exemplary, safety record. Since the inception of the so-called second-generation tramways in Manchester back in 1992, no passenger had been killed in an accident on board a UK tram.
Modern tramways in the UK have become incredibly successful in the towns and cities where they have been implemented. They are an effective and efficient people mover, operating high-frequency daytime services on densely populated routes, with millions of commuters and leisure travellers relying on trams as their chosen mode of transport for work and leisure.
However, when the Rail Accident Investigation Branch (RAIB) revealed the following week that the Croydon tram had been travelling at more than three and a half times the permitted line speed at the point it derailed, the safety of trams in the UK came to the fore. How could this have happened? And more importantly, what action could be taken to ensure a similar such accident can never happen again?
Following the Sandilands accident, Tram 2551 was removed to a secure RAIB facility, where it has been tested and examined in detail, to learn as much as possible about what went wrong on that November morning just over a year ago.
The tram involved in the accident was Bombardier CR4000 tram 2551, one of the original 24 trams built for Tramlink in 1998 in Austria. To increase capacity and enhance services on the network, a further 12 Stadler Variotrams entered traffic with London Tramlink between 2012 and 2016.
Following the Sandilands accident, Tram 2551 was removed to a secure RAIB facility, where it has been tested and examined in detail, to learn as much as possible about what went wrong on that November morning just over a year ago.
London Tramlink (originally known as Croydon Tramlink) opened in May 2000. It is owned by Transport for London under the London Trams banner and operated by FirstGroup subsidiary company Tram Operations Ltd. The system carried more than 29.5 million passengers during the year 2016-17 and has become one of the leading UK tramways in terms of its usage and popularity, partly due to its location in the London commuter belt.
One significant aspect of tramway operation that differs from conventional railways is that the majority of UK tramways are operated on line-of-sight principles (similar in many ways to driving a car), rather than operating under the control of railway-style block signalling - although major junctions and single-line sections are usually controlled by signals to prevent conflicting moves by trams. Road junctions are also signal-controlled, with the tram signals performing similar functions for tram drivers to how traffic lights are provided for motorists.
Modern trams are much lighter than a conventional train, allowing them to have much quicker acceleration and braking than a train. The light-rail nature of tramways also means that more frequent station
Following the accident at Sandilands, Tram Operations Ltd is now trialling a form of motion detector to try to identify when a driver may lose alertness while driving.
stops can be provided than on a typical rail route, allowing them to serve more local communities.
While they run on rails and are powered by overhead electrification (although Midland Metro is soon to trial batteryoperated catenary-free running on parts of its forthcoming extensions), in many aspects they are similar in the way they are operated to the bus industry.
Trams are operated solely by a driver (although some operators employ on-board conductors to collect revenue). The driver is responsible for the safe operation of all aspects of the tram under his control. With system route knowledge provided during their initial training, drivers are expected to know speed limits applicable throughout the routes they drive, the points where they need to brake for speed restrictions, and the areas where potential hazards may be encountered. With trams also operating on-street, drivers also need to be alert to the additional hazards of pedestrians and motorists in these areas.
Up until November 9 2016, the line-of-sight driving principles applied to tramways had proved to generally work well. It is suited to the types of heavy-frequency services that are operated. Trams can be allowed to travel closely behind each other, with drivers controlling their vehicles in much the way a motorist controls a car, being aware of the various factors that could make them intervene to slow or stop the tram if necessary.
Only Metrolink in Manchester was fitted with traditional red/green railway-style block signals on its segregated off-street sections, when it opened in 1992. But as that tramway has been expanded, it too has adopted the line-of-sight principles on most of its routes, to bring it in line with the other tramway operators around the country. Eventually, the entire Metrolink system is intended to be operated under the line-of-sight model.
Modern trams are fitted with on-tram data recorders (OTDR) that record every aspect of their performance while they are in motion - acceleration, speed, braking, application of hazard brakes, the sounding of the horn and bell, and so on. Scrutinising 2551’s OTDR gave RAIB sufficient information to enable it to release its first interim update into the accident
just seven days after the derailment.
Almost all public transport vehicles, including trams, now make widespread use of on-board CCTV cameras. Typically, this includes outward-facing cameras in each cab, along with a number of internal cameras in the passenger saloons. In most cases, these CCTV systems are used by the operators in the event of claims following accidents, as well as for investigating other incidents which may occur.
However, following the Sandilands derailment, it was discovered that the CCTV system fitted to Tram 2551 had not been functioning correctly at the time, and the incident had not been captured on the tram’s CCTV hard drive. Had this been functioning, the task of reviewing what had happened in the lead-up and aftermath of the accident would have been much easier for the investigators.
The CCTV system had failed to record the incident due to a defective hard drive recorder. At the time of the accident a project was under way to evaluate new, more modern, CCTV systems which could be used on the trams. These have since been fitted to the London Tramlink fleet.
On November 9 2016, Tram 2551 left the previous tram stop at Lloyd Park and travelled along a long straight section of line that also contains three closely spaced tunnels.
This straight section is operated by trams running at the maximum line speed of 50mph, before slowing for the sharp curve at Sandilands Junction. Here there is a 12mph speed restriction, due to the tight 30-metre radius curve where the line leaves the segregated part of the tramway at Sandilands Junction, before going on-street towards Croydon town centre.
Having accelerated to the maximum line speed of 50mph after departing from Lloyd Park tram stop, Tram 2551 continued at maximum speed as it headed towards
Sandilands Junction. RAIB has concluded that after leaving Lloyd Park the driver lost attention for a period of several seconds, possibly due to going into a microsleep. RAIB suspects that when he regained awareness, he was disorientated about his exact location and didn’t realise how close he was to the junction in time to react appropriately.
We’ve all seen the electronic signs on motorways, instructing us ‘Do not drive tired’. But with the RAIB concluding that the driver of 2551 probably went into a microsleep just before the accident occurred, this message now has a particularly poignant meaning for the tramway industry.
In February 2001, at Great Heck on the East Coast Main Line, ten people were killed and 82 injured when a GNER train struck a Land Rover and trailer that had fallen onto the track from the adjacent M62 motorway, causing the GNER Class 91 locomotive to partially derail before colliding with a Freightliner coal train hauled by a Class 66 locomotive heading in the opposite direction. Both train drivers were among the dead.
The accident at Great Heck was caused when the driver of the Land Rover fell asleep at the wheel of his car. It drifted off the road and down the embankment, setting in motion the tragic chain of events.
There have been countless other road accidents caused by drivers falling into a microsleep - fatigue and tiredness are acknowledged as being very difficult to manage, as it requires the individual to accept that they are not fit to drive their vehicle.
Following the accident at Sandilands, Tram Operations Ltd is now trialling a form of motion detector to try to identify when a driver may lose alertness while driving.
The analysis of the OTDR on Tram 2551 showed that a brake application was not made until two seconds before the tram derailed, by which stage there was no time to prevent the tragic set of events that were about to unfold. The tram had not slowed sufficiently as it entered the curve, and overturned while travelling at 45mph. Through calculations and simulations, RAIB established that the tram would have overturned had it been travelling at any speed greater than 30mph.
Trams in the UK are fitted with electromagnetic track brakes, which clamp large magnets to the tracks from the bogies when the driver makes an emergency brake application. The application of the emergency brakes (also known on some tramways as a hazard brake) helps to dramatically increase the braking force of the tram in an emergency situation.
In the Sandilands accident, the emergency brake was not applied by the driver, indicating that he either did not have time to react when he realised what was going to happen, or that he thought the service brake would slow him sufficiently. RAIB concluded that had he applied an emergency brake application instead of the service brake, it is possible that the tram may not have overturned.
During its investigation, RAIB examined another incident which had taken place just a few days earlier - on October 31 2016. A passenger complained to Tram Operations Ltd about an incident where they encountered a tram going too fast around the same Sandilands curve, which had caused them to be unseated as the tram entered the curve. Loop data from the area was analysed and found that this incident had also had the potential for the tram to have overturned. Thankfully it didn’t.
While it is not believed that a culture of speeding existed on the Tramlink system, RAIB was critical that there appeared to be a lack of understanding as to the potential risks associated with the possibility of trams overturning if travelling too fast around sharp curves.
While the glazing was found to be compliant with UK standards, it was not strong enough to prevent breaking when people fell against it as the tram started to overturn.
From 2003, the wider railway network adopted the fitting of a train protection and warning system designed to slow a train in the event of it approaching a signal at danger, or if it is travelling too fast approaching a speed restriction. The system intervenes if the driver does not react to an approaching hazard.
RAIB is recommending that a similar system be investigated for use on tramways, in order for the technology to intervene should a driver be found to be travelling excessively fast towards a speed restriction. Transport for London is currently investigating such a system for Tramlink, and other operators will no doubt be observing developments.
The report also recommends additional visual trackside signage to assist drivers approaching sharp bends, similar to the chevron signs fitted on roads. These have now been installed at Sandilands Junction.
The driver in the Sandilands accident regularly worked early shifts at Tramlink and did not believe that he was fatigued prior to the accident, although the RAIB was critical of some of the rostering which could contribute to drivers suffering from fatigue.
Another recommendation to come from the RAIB report is the strengthening of tram windows and door glazing, to match the standards of glazing currently used in standard rail vehicles. Tragically, those killed in the accident died as a result of being ejected out of the tram as it overturned, suffering crush injuries as 2551 toppled over. A number of the other passengers who were seriously injured sustained their injuries after being partially or fully ejected through the tram windows and doors.
While the glazing was found to be compliant with UK standards, it was not strong enough to prevent breaking when people fell against it as the tram started to overturn. RAIB believes that these people may have been better protected if tougher glazing had been fitted to the tram, although the glass still has to be capable of being broken in the event of an emergency that may necessitate evacuation from the inside of the tram.
Another issue which added to the distress of those involved in the accident was that when 2551 overturned, an external switch was operated as the tram hit the ground. This isolated all power to the vehicle, and meant that the emergency lighting inside the passenger saloon failed to operate.
Cross-industry co-operation is also one of the key messages coming from the RAIB report. It encourages more dialogue between the owners and operators of the systems to share knowledge and experience, particularly in relation to safety aspects of the tramways that could be adopted by other operators.
In total, RAIB made 15 recommendations aimed at improving the processes and procedures of the tramway industry, as well as items specific to Transport for London (London Trams) and Tram Operations Ltd that were discovered as a direct result of the Sandilands investigation.
The accident at Sandilands Junction has brought tram safety to the fore, and while this is the first serious accident on a UK tramway to involve loss of passenger lives, it has also highlighted a number of issues that the tram industry must now examine and address.
Tram travel in the UK is still one of the safest forms of public transport available, but the industry cannot afford to be complacent. No one ever wishes to see again such tragic images as we witnessed on November 9 2016.
It encourages more dialogue between the owners and operators of the systems to share knowledge and experience, particularly in relation to safety aspects of the tramways that could be adopted by other operators.