Fire in the Hole: The 2008 Channel Tunnel (France/England) Train Fire
Background
The Channel Tunnel (also referred to as “Chunnel” on occasion) is a 50.46km/31.35mi railway tunnel connecting England and France beneath the ground of the English Channel at the Strait of Dover. Opening in 1994, over 190 years after the idea was first proposed, the tunnel consists of two single-track tubes dug beneath the seabed along with a service/evacuation tunnel between them measuring 4.8m/16ft in diameter. The three tubes are connected by several access passages along with 2m/7ft wide piston relief ducts, inaccessible ventilation shafts designed to handle the change in air pressure when trains move through the outer tunnels and act like pistons in an air pump. The tunnels also feature 2 undersea-crossovers which can be used to let trains cross from one tunnel to the other if needed, any other time the crossovers are sealed off with airtight doors. The service-tunnel is home to a fleet of double-ended specialty rescue vehicles which are configured as either buses to transport responders and survivors or as emergency response vehicles carrying firefighting equipment. These vehicles are not fully autonomous but drive along a magnetic line to help drivers stay clear of oncoming vehicles and the tunnel walls.
Despite being above ground the remaining sections of the rail line between the tunnel and the terminus stations are also referred to as part of the tunnel rather than getting their own name as a rail line going through the tunnel along the way. The tunnel sees both passenger and freight services, largely provided by Eurostar high speed trains or special car carrier trains (branded “Le Shuttle”) which carry cars and motorbikes in enclosed train cars or trucks on open low-floor freight cars. All services through the tunnel are provided by electric trains, being fed 25kV from overhead catenaries and reaching speeds of up to 160kph/100mph. The only exceptions are maintenance trains and tow-locomotives to rescue stranded trains, which are diesel-powered. The trains carrying cars and trucks through the tunnel have a unique loading gauge larger than that of English or French railways and thus cannot travel beyond the shuttle-service’s end stations at Coquelles (France) and Cheriton (England) while Eurostar high speed trains can and do.
The train involved
Freight Shuttle 7412 was a southbound shuttle train carrying 25 trucks and two delivery vans from England to France. Each freight shuttle train consists of a locomotive on either end, an “amenity car” passenger car for the truck drivers behind the leading locomotive and several low-floor carrier cars for the trucks. The amenity car, where the drivers are required to stay during the trip, measures 25.72m/84ft in length while the carrier cars measure 20m/66ft in length. A regular freight shuttle like the one involved in the accident measures 775m/2540ft in length, including the two locomotives. While the first generation carrier cars had a full-length roof the second generation carrier cars featured short roofs above the trucks’ cabs, but those were removed in the early 2000s due to structural concerns, leaving the trucks fully out in the open on that type of car.
Each train features a Eurotunnel Class 9 locomotive on either end, acting similar to motor cars on high speed train and allowing identical performance in either direction (although the trains turn around at the terminals via a 180°-turn rather than changing direction in a dead-end track). The Class 9 was developed specifically for the trains through the tunnel, using the narrow gauge EF-class locomotives found in New Zealand as a base. Each class 9 measures 22m/72ft in length at a weight of 132 metric tons and can reach a top speed of 160kph/100mph. The six-axle locomotives feature several oddities, such as CCTV-feeds from several cameras aboard the train and a special driver’s desk that can be operated both standing and seated as French drivers usually prefer the latter while English drivers prefer the former. The driver’s cab is also pressurized and climate-controlled for increased comfort as the trains speed in and out of the tunnel. While only one full drivers cab is fitted the rear, “blunt” end also features basic driving controls used for shunting. A second seat in the driver’s cab intended for the “train captain” is rarely used in the leading locomotives, with the captain instead usually sitting in the rear locomotive, observing the CCTV-feeds, making announcements and being prepared to push or back the train out of the tunnel in an emergency that incapacitates the driver on duty.
The accident
On the 11th of September 2008 at 3:15pm a new crew takes over the freight shuttle that is to be service number 7412 from England to France. During the handover the leaving train captain informs his successor that door 3 of the amenity car is defective and has been disabled, leaving the 3 other doors functional. The train departs the english terminal at 3:36pm, right on schedule, with 32 people on board, including 3 crew members. For unknown reasons the train captain is travelling at a workstation at the back of the amenity car instead of manning the rear locomotive.
Shortly after entering the tunnel a power-spike in the catenary trips the breakers, cutting power to the overhead catenary and bringing the train to a stop. Both the control center staff and the train driver are unable to find a reason for the incident, and thus the control center resets the breakers and allows the train to proceed with its journey, be it at a reduced speed of 100kph/62mph.
At approximately 3:50pm, just after passing the halfway point of the tunnel, the train captain hears a brief unusual noise, later described as a dull and quick boom. The occasional odd noise by itself is nothing concerning and thus the captain chooses not to raise an alarm about it. 4 minutes later, at 3:54pm, the smoke detection system aboard the train is tripped, setting off an audible alarm and reporting smoke at the rear of the train. Looking through the window at the end of the amenity car the captain spots flames coming from one of the vehicles loaded onto the train and reports the fire to the driver via the intercom before closing off the car’s ventilation system as mandated by safety protocols, keeping smoke from entering the train car if the train stops for an evacuation.
After informing the driver of the fire a minute passes without the train slowing down, leading the captain to notify the driver again, urging him that there is definitely a fire and the train MUST stop. The captain and several passengers later recall seeing the leading truck outlined against the flames, indicating that the fire is burning at the rear of it or behind it, but not too far down the train. Several witnesses also recall hearing explosions, with the investigation, unable to find any sign of an actual bomb, later concluding that the noises came from tires and fuel tanks bursting.
By 3:56pm the train is finally slowing down while the captain starts handing out breathing masks to the passengers. He tries to instruct the passengers on the correct usage of the mask with little success, as several passengers are becoming nervous and agitated, moving around and standing in the central isle and thus blocking sightlines to the front of the car. The train stops at 3:58pm right at a marker intended to line up the amenity cars’ doors with an emergency exit towards the service tunnel. Smoke is now surrounding the train, but due to the closed off ventilation system does not enter the train. The captain can’t see outside the train car, he also doesn’t know if the driver forwarded the alarm to the control center and thus can’t tell which emergency exit they are at or if the exit will be opened by control center staff. Communication with the increasingly restless passengers is also handicapped by the breathing masks along with the captain speaking almost no French while most of the passengers speak no english and in 60% of cases no or only very poor english or french, coming from countries with other languages.
At 4:01pm passengers start trying to open the doors at the forward end of the car, right as the driver passes train control to the captain. They first try the forward right hand door, which is locked, before turning their focus to the left hand door. Usually the captain would be positioned at the forward end of the car during the evacuation, but due to the blocked aisle he has been unable to go there. Five passengers manage to open the forward left hand door and leave, with one quickly returning. Luckily the command center opens a nearby passage to the service tunnel at just that moment, with the overpressure from the service tunnel creating a small air bubble that prevents smoke from immediately flooding the train car. Normally the door of the amenity car should be perfectly lined up with the passage, but due to an error in the instructions for train drivers the train slightly overshot its ideal position, ending up about 4m/13ft out of alignment. The passage is also to the right of the train, and the group of passengers chose to exit to the left.
Further Passengers then proceed to ignore the captains instructions to follow him out the right hand door at the back of the car and instead use the provided hammers to break a window lined up with the passageway, climbing through it after one of the passengers kicks out the remaining glass. By 4:06pm the captain reaches the passageway into the service tunnel, arriving after the passengers who climbed through the window. The four passengers who left through the left hand door are still in the tunnel, moving towards the front of the train, while the driver is still in his cab.
Protocol demands that the driver remains in his cab, safe from the smoke, until smoke clears enough that he can see the handrail of the catwalk along the wall of the tunnel. The driver of 7412 cannot see the rail through the thick smoke, but as time passes he gets increasingly worried about becoming a sitting duck in the stranded train with conditions outside not improving and the fire possibly making its way up the train. After being reassured by control center staff that the nearby passageway is open he leaves his cab at 4:06pm, wearing a breathing mask and crawling along the floor due to nonexistent visibility. He reaches the passageway 2 minutes later, just as the tunnel’s ventilation system starts clearing the smoke.
The four passengers still in the tunnel have split up in the meantime, two of them return to the train car and make their way to the passageway, arriving 10 minutes after the driver. The other pair continues further towards France, eventually giving up and turning around also after covering 340m/1115ft in the thick smoke. By pure luck they come across a second open passageway (opening two passageways is standard protocol to pump more fresh air into the affected tunnel) at 4:26pm and are picked up by arriving responders before being reunited with the other passengers, allowing responders to call off a search. After being evaluated at the site the survivors are taken to the relatively nearby French exit of the service tunnel. By 6:44pm the driver, captain and catering steward reach the portal of the service tunnel by car, being the last people off train 7412 to leave the tunnel. Everyone aboard the train survived, with 14 people being treated for minor injuries like smoke inhalation and bruises. 11km/6.8mi behind them the train is still burning, reaching temperatures exceeding 1000°C.
Aftermath
Over 300 firefighters from France and England battled the blaze in the tunnel for the next several hours, reportedly extinguishing it by 6am the next day and finally leaving the tunnel a few hours later, having handled several “hot spots” that could have re-ignited the fire or kept smoldering on their own. The firefighting effort was slowed by a truck close to the origin of the fire supposedly carrying 100kg/220lb of carbolic acid, a toxic, flammable chemical used in the pharmaceutical industry. It was only after the fire was extinguished that the information was corrected from 100kg to about 100g/3.5oz. Several train cars, 2 trucks upon them and the amenity car were destroyed in the blaze while further cars, vehicles and the locomotives were damaged by smoke and heat. 650m/2130ft of tunnel wall also had to be replaced after the fire.
This had been the third fire aboard a freight shuttle inside the tunnel, and the second one that consumed the train and forced prolonged closure of the tunnel. The previous severe fire had taken place in November 1996 and had later been traced to arson. Investigators set to work, first examining the tunnel and the remains of the train for any sign of a bomb or another device that could have deliberately started the fire. In the meantime police on the English side started “operation stack”, a protocol that handles the traffic backup from a closed tunnel by closing the nearby M20 motorway and using it as a linear parking lot for the trucks unable to use the tunnel.
Unable to find any sign of a deliberate ignition the investigation turned its attention to the train and its cargo itself, and soon to the trucks loaded onto the burned train. Looking over CCTV-footage of the train ahead of the fire they spotted the drivers cab of the truck on train car number 15 filling with smoke approximately 23 minutes prior to the smoke alarm on the train being tripped. There was nothing in the truck’s cab that could produce high amounts of smoke by itself or even start a large-scale fire, but the investigators at least knew that they were on the right path. Looking through the tunnels data-logging system they confirmed that the smoke accumulation occurred shortly after the power-spike had brought the train to a stop.
The investigators turned their attention to the path of the truck until it ended up on car 15 in the tunnel, tracing its way back to the loading-procedure at the english terminal. A camera at the platform had captured the affected truck driving onto the train and showed a thin aerial sticking up from the cabin roof beyond the height of the trailer. Trucks using the train had to adhere to a height-limit of 4.2m/14ft, originally to fit under the car roofs and later to ensure sufficient distance of any part of the truck to the overhead catenary. This was ensured by an automatic “aerial detection system” meant to flag anything protruding past the limit as trucks go past it. In addition to that the loading agents were instructed to watch for protruding elements, be it aerials, lamps, decorations or cargo. One of the loading-agents had actually spotted the aerial on the affected truck, but, due to being inexperienced, chose to consult a coworker before holding the load-process. The coworker, a more experienced loading agent, told him that the truck had already passed the detection system without triggering it and thus that the aerial probably just looked higher than it was.
The investigators consulted the manufacturer of the affected truck and recreated the situation at the terminal, finding that the system usually flagged the test-truck but did not do so every time it went past. Slowing the truck down increased the hit-rate, leading to the conclusion that the usual speed of the trucks passing the system was so high that the thin aerials either bent down below the limit or simply appeared in the “excessive” area too briefly to be reliably detected. The loading agent was not blamed for the ensuing events as consulting experienced coworkers was seen as a sensible option ahead of holding up operations.
The investigation concluded that the truck’s aerial was clearly past the height-limit for trucks using the train and thus made contact with the overhead catenary just past the english portal where the catenary is at its lowest point. This created the initial power-spike which brought the train to a stop. There was no rule requiring the train to be examined after such an event, a simple check of the train’s onboard diagnostics and checking for visible smoke/fire was sufficient to allow operations to resume. Had the train been barred from resuming motion and the catenary been left off the fire would not have occured, at the price of one of the recovery-locomotives needing to tow the train back out of the tunnel. But once the catenary was energized again the aerial on the truck continued to create an electrical arc which eventually set fire to the truck, which led to the ensuing inferno.
There is actually a way to extinguish small fires on the trains without completely stopping operations, with 2 so-called “SAFE”-stations being installed in each tunnel. Each of these stations consist of an 870m/0.5mi section of the tunnel fitted with a powerful water-spray system above and on either side of the trains designed to cool down/extinguish hot spots and small fires. These stations do not start up automatically but on command from the control center, and could have likely handled the early stages of the fire aboard train 7340. The train had entered the last such station on its journey shortly after the alarm on the train was tripped, but was already past it by the time the train driver brought the train to a halt. Technically, a very fast reaction by the train captain, driver and control center staff could have meant that the system would have activated in time to spray down the burning truck halfway down the train.
The southern tunnel reopened to trains two days after the accident, with the northern tunnel only returning to full capacity in February 2009. In the aftermath of the fire 4 more SAFE-stations were installed in the tunnels, two per tube, and emergency evacuation instructions are now displayed in the amenity car in 9 languages. The operator of the tunnel also announced that firefighting protocols would be improved as it took over an hour between the fire being detected and firefighting to start in full force, during which time the ventilation system fed oxygen to the fire and thus increased damage. It was also announced that the aerial detection system would be overhauled. The new SAFE-stations became operational in January 2012. In the end so many small things contributed to the fire that no single individual was ever held legally responsible.
Since the 2008 fire the freight shuttles have caught fire two more times, once in 2012 with the train driver managing to pull the train out of the French-side portal before stopping and one in 2015 that required an evacuation within the tunnel.
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