Background
Croydon is a suburb of London (population in 2011: 192064), England, located 14.5km/9mi south of downtown London and 30km/19mi north of Crawley in southern England.
The city is the center of a Tram-system (operating under “London Trams” or “Tramlink”-Branding), serving 39 stations in Croydon and the surrounding area via 28km/17mi of track. The system opened in May 2000 and saw 27.2 million passengers by 2020. Trains reach up to 80kph/50mph during service, running both on rails integrated into roadways and separated sections with traditional sleepers and ballast.
The train involved
On the day of the accident the 5:53am service from New Addington to Croydon Town Centre was provided by Tramlink train number 2551, a Bombardier CR4000. Introduced in 1999 the CR4000 is a two-car electric multiple unit designed for Croydon’s tram services, based off the K4000-series in service at Cologne (Germany). Each of the 24 units built measures 30.1m/99ft in length at a weight of 36.3 metric tons. The trains can carry 70 seated and 138 standing passengers at up to 80kph/50mph, with 76% of the interior being set up as a low-floor area for barrier-free usage by strollers, wheelchairs and passengers with limited mobility. At the time of the accident the train carried a driver and 69 passengers.
The accident
On the 9th of November 2016 tram number 2551 departs New Addington station perfectly on time at 5:53am with a 42 years old driver and 26 passengers on board. Heavy rain is drumming on the windows of the tram as it makes its first five stops ahead of the city of Croydon, collecting another 43 passengers by the time it departs Lloyd Park station. A sharp right hand turn brings the tram in alignment with a former railway line, where the it accelerates to its 80kph/50mph top speed as it dives into a tunnel. the tram will leave the old railway line’s path 600m down the line, intersecting with the line from Elmers End in a sharp left hand turn. The intersection has a speed limit of 20kph/12mph.
The driver fails to start reducing the tram’s speed in time, reaching a sign marking the 20kph/12mph speed limit at 6:07am while travelling at 78kph/48mph. The driver applies the brakes at that point, but only manages to shave off 5kph/3.1mph before the tram enters the turn, leaving it no chance to make it through the intersection. Centrifugal forces almost immediately overcome the tram’s weight, causing it to lean in excess of 45° to the right before the leading axle derails. The tram subsequently falls onto its right hand side, shattering almost all windows on that side of the chassis. 7 people are partially or fully ejected through the created openings and suffer fatal injuries in the process. All remaining 62 people on board are injured, 19 of which severely. The tram finally comes to a stop halfway through the turn, just 135m/445ft ahead of Sandilands station, after sliding 27m/89ft on its side.
Aftermath
The first person on site is the driver of an oncoming tram which had been stranded just past Sandilands station when the derailment caused power to be cut. Several survivors place calls to the emergency services after the accident, while the two drivers use a fire extinguisher and a metal bar to create an opening in the windshield that survivors can be evacuated through.
Within 10 minutes of the accident 70 firefighters, 21 ambulance-crews and several dozen police officers are involved in the rescue-effort, assisting survivors out of the train and down the line towards Sandilands station where ambulances are waiting. 51 people are taken to surrounding hospitals, with another 7 being released at the site only to make their way to a hospital independently. Originally responders report 5 victims, it’s only through witness statements and personal belongings that the presence of 2 more people onboard can be determined as their bodies are completely hidden by the overturned tram. The derailment is the deadliest tram-accident in the UK since 1917 and the UK’s deadliest rail accident since the Great Heck Train Crash claimed 10 lives in 2001.
The tram is uprighted two days after the accident and removed from the site on the 12th of November to be further examined elsewhere. Uprighting the tram also allows the recovery and eventual identification of the last victims. It takes until the 18th for repairs to the track and surrounding infrastructure to finish so that the intersection can resume service at full capacity. The driver, who was initially arrested on the day of the accident, is eventually released on bail as he doesn’t pose a flight risk.
Investigators find that the speed limit sign, placed beyond the exit of the tunnel, wasn’t visible to drivers until they were 90–120m/98–131yd (depending on conditions) past the point where they would have had to start slowing down. When FirstGroup, the company operating the trams under contract, is questioned about the situation they explain that drivers were expected to know where to slow down from experience on the route. The recovered data-logger shows that the tram had approached the intersection at wildly excessive speed after the driver first gave a slight brake-input but eased off, maintaining nearly unreduced speed until he tried to slow down immediately ahead of the turn.
The investigation finds that the track and tram had been in perfect working order, declaring the cause of the derailment to be human error by the driver. The signage (or lack thereof) is sharply criticized, with Tramlink following the recommendation of placing additional signs in the tunnel ahead of the intersection. The scarce signage and absence of a train control system had been legal though, as trams don’t count as railways under UK law. They carry their own legal status, which is closer to buses.
A new spin is put on the events preceding the accident when a former driver gives a statement to a newspaper, saying drivers had to follow erratic shift-patterns and the depot’s break room only offered a vending-machine filled with energy drinks, which could have led to the fatal lapse in attention:
“Nobody is ever fully awake; I was always in a bit of a daze and that is because the way the shifts work doesn’t allow the drivers to get a regular sleep pattern.”
Following the driver’s statement to the newspaper a video starts circulating which seemingly shows a tram driver struggling to stay awake at the controls, prompting a separate investigation by Tramlink. The article also prompts an investigation by “Victoria Derbyshire”, a news-program produced and aired by the BBC. The program publishes their findings in April 2016, revealing four cases of tram-drivers falling asleep at the controls by suffering episodes of “microsleep”, a phenomenon where the individual falls asleep for no more than a few seconds without prior warning.
Transport for London, the parent-company of Tramlink, accepts liability for the accident in March 2017, meaning survivors and victims’ relatives won’t have to sue for compensation. By November of that year fatigue monitoring devices are installed in the driver’s cabs, which use infrared light to observe the driver’s face, feeding the footage to a software which can spot signs of lacking attention/excessive fatigue and activate a vibration-module in the driver’s seat. The introduction of the system sparks 2 days of strikes by tram drivers, who don’t want a “spy in the cab” and point out concerns about consequences regarding the driver’s health. The latter concern is quickly silenced when it’s pointed out that the infrared-radiation used is less than 2% of the infrared-radiation one is exposed to by being in sunlight.
A parallel branch of the investigation looks into the questionable crash-safety of the C4000, pointing out how there likely would have been no fatalities had the tram not lost nearly all its right-hand windows. The report explains that the tram was built to the safety-standards of a city bus rather than a train, which led to toughened glass being used instead of laminated glass. The windows were fitted with a plastic film on the inside, mostly meant to limit vandalism, which offered some connective strength, but the result was not comparable to laminated glass which the tram would have had been equipped with if railway safety standards would apply.
In the end blame for the accident is placed on the driver, who failed to obey the speed limit likely because of a phase of microsleep. Tramlink (and by extension Transport for London) are urged to address shift-pattern issues, improve signage for speed limits and evaluate the introduction of an autonomous system to control the speed of their trains. Such a system, while standard on regular railways, was not required on tram lines as those usually operate at slower speeds, have stronger brakes and are run with more responsibility on the driver. This is because trams, in contrast to regular trains, usually can’t assume that there won’t be obstacles in the train’s path to react to. This “line of sight”-operation is the main justification for not requiring a secondary system to observe train speeds.
Transport for London reacted to the findings by replacing the 100μm (0.1mm) thick plastic film on the tram windows with a 175 μm thick version to improve containment, installing further signage ahead of speed limits throughout their network, and, by 2019, install a speed surveillance system at “high risk locations” on the Tramlink-network which will autonomously apply the brakes if a tram approaches the high risk spot at excessive speed. Tram- and Metro-systems in several other cities in the UK also adopted the improved signage-pattern introduced at Croydon.
Two memorials to the accident exist today, one at Sandilands station and one at New Addington. Both consist of a light gray stone pillar reminding visitors of the accident, with the one at Sandilands station listing the victims by name.
After the initial investigation against the driver regarding negligent manslaughter ended with no charges filed due to lack of criminal guilt charges were filed after all in March 2022, accusing him of “failure to take reasonable care of passengers”. Charges were also filed against Transport for London over “failure to ensure the health and safety of passengers”. The trial started on the 10th of June 2022, with Transport for London’s representative pleading guilty while the driver pled not guilty. As of writing this (April 2023) the proceedings appear to be ongoing.
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