Background
Berlin is a city of 3.78 million people (as of 2023) in the far east of Germany, 125km/77.5mi east-northeast of Magdeburg and 146km/91mi north of Leipzig (both measurements in linear distance). The German capital is its own federal state, being entirely surrounded by but separate from the state of Brandenburg.
Being both the capital and largest city of Germany (by a margin of almost 2 million people) creates a high demand for transportation, leading to Berlin being crisscrossed with an expansive network of tramlines, subways, commuter- and regular rail lines alongside the road network and several airports. One of these rail lines is the Berliner Stadtbahn (“Berlin City Line/Train”), a quad-tracked electrified elevated rail line running east to west through downtown Berlin as it somewhat follows the Spree river.
The 11.2km/7mi line was opened in 1882, being meant to offer a fast connection between several terminus-stations from different rail lines spread around the city. Two of the four tracks were intended for long distance trains while the other two were for regional/commuter trains, a pattern still followed today as two tracks belong to the S-Bahn (an urban commuter rail system).
Berlin-Bellevue Station, named after the nearby Bellevue Palace (the residence of the German president) is a double-tracked commuter rail station opening in 1882. The station’s two tracks are used by the S-Bahn trains, with the regional and long distance trains passing the station on its southern side. The next station to the east is Berlin main station 1.5km/0.9mi up the line, the next station to the west is Berlin-Tiergarten 1.1km/0.7mi down the line.
The Train Involved
DPE 86363 was an irregular passenger service from Berlin to Freiburg in the far southwest of Germany. The train had been chartered by the “Support Crew Freiburg”, a fan-group of Freiburg’s soccer team, and had shuttled around 700 fans to a soccer game in Berlin before being supposed to take them back home after the game. Both the train and locomotive were owned by the Swiss Centralbahn AG, a rail service provider specializing in chartered trains, usually with older rolling stock that had been retired by the German national railway (DB).
The train involved in the incident consisted of a German class 110 electric locomotive and 13 four-axle express passenger cars of different types. The second car was a type Am208 first class compartment car made in 1954, numbered 56 80 10–40 122–8. The type has its interior split into 10 compartments for six passengers each for a total capacity of 60 passengers. It has an empty weight of 37 metric tons at 26.4m/87ft and is allowed to travel at up to 140kph/87mph.
The Fire
The train had delivered the Fans to Berlin around noon on the 19th of October 2019 and had then been parked empty at Berlin-Grunewald station pending the return trip in the evening. The dispatcher at Grunewald station spotted “light smoke” on the second car at 6:02pm and ordered the driver to check what was going on. The driver radioed back at 6:12pm that the smoke was merely steam from the train car’s heating-system, explicitly stating that nothing was burning.
The train eventually departed for Berlin-Charlottenburg station, where it would pick up the fans, at 7:08pm, 20 minutes before schedule so that there would be more time for the fans to board. It’s unknown at which time the train was meant to depart Charlottenburg station, but it did so on a slight delay at 8:01pm as some fans had arrived at the platform late. The train departed Charlottenburg station to the east, planning to head south on the eastern side of Berlin.
However, the driver radioed the local dispatcher at 8:05pm and reported that he had a fire on the train and that he was bringing the train to a controlled stop at the S-Bahn station Bellevue. He also asked the dispatcher to alert the fire department to that station. The train came to a stop at Bellevue a minute later, with the driver reporting a danger to operations (standard procedure in such a case) which led to the line being completely shut down. He also notified dispatch that passengers were on the tracks as they had evacuated the train and were walking along the rails to the station building. The S-Bahn tracks were only officially shut down by 8:12pm, at which point the high-voltage third rail (which runs alongside the tracks) was powered down. Luckily none of the evacuating passengers came in contact with it before that. Arriving firefighters found the train’s second car “in full burn” upon their arrival and began setting up to extinguish the blaze while also assisting the federal police in evacuating the trains and platform.
Aftermath
Both the 760 fans aboard the chartered train and passengers from two S-Bahn trains at the station were evacuated by 8:32pm. 3 people were taken to the hospital for smoke inhalation, a fourth patient was treated on site and released. The fire was extinguished by 9:40pm, having gutted most of the train car but without spreading to the adjacent cars. The station building, which is a protected historic site, also remained unharmed.
The fire department complimented the fans’ behavior the day after the fire, explaining how they had been calm and followed orders, making it possible to quickly get the whole group to safety. However, the fire department did point out that one should avoid exiting a train on their own due to the dangers from rail traffic, third rails or the overhead catenary (which can snap and fall in a fire).
The car which had suffered the fire itself was fairly obviously a full loss, while adjacent cars suffered damage from smoke contamination and firefighting materials. The heat from the fire had been so great that it weakened the frame of the burning train car, causing the whole thing to sag down in the middle.
One of the fans started rumors about the cause of the fire within an hour of the accident, telling reporters “and that after we’d been told not to light Bengalos on the train!” Bengalos are a type of flare popular with soccer fans, which create a bright (usually red) light and a considerable amount of smoke. They are highly controversial as they burn at 1600–2500°C (2900–4500°F), are bright enough to harm the eyes when looking right at the flame, and are incredibly difficult to put out/keep extinguished.
One of the train trip’s organizers told the media that they first got a lot of smoke in the forward part of the train, but that she didn’t see anyone handling pyrotechnics in the train and didn’t think that a Bengalo caused it. The SID (Sport-Informationsdienst/”Sport Information Service”), a news agency, claimed that the fire had been started by a technical defect instead, which was rejected by the Centralbahn. They stated that the fire had started in the interior of the train in the train car’s center, where there isn’t any technical equipment which could cause a fire. The rumor that the heating system could have caused the fire was rejected as “the heating is under the car’s floor, there’s only hot water piping in the interior”.
The investigators weren’t quite so quick to reject the heating system as a cause, initially stating that the remains of the train car didn’t allow immediate rejection of that theory. The Am208 is fitted with a gravity-based heating system using a mixture of 2/3 water and 1/3 Glysanthin G48 antifreeze. The water is first run through a heat exchanger beneath the car’s floor, where it is either heated by 72 electric heating coils or integrated steam tubes, depending on whether the locomotive can provide electricity or steam for heating. The hot water then runs through radiators in the compartments, the aisle and the two bathrooms, losing its heat as gravity directs it back to the heat exchanger. A separate pipe runs from the heat exchanger to the expansion tank, which is meant to absorb the expansion of the water that happens due to the changes in temperature. The water-level in the pipe up to the expansion tank operates a small lever which connects two electrical contacts. Those two contacts would disconnect if the water level dropped too low, shutting the heating coils off so it wouldn’t heat an empty system.
Later units of the same type were also fitted with a high temperature shutoff, which would cut power to the heating coils if the water in the heat exchanger exceeds 130°C/266°F, but this train car didn’t have that system.
Water overflowing from the expansion tank goes to a separate retainer-tank from where it could be pumped back into the system if needed, if that one overflows it would vent/drip to the outside.
The heating-system is supplied with different voltages from 1000 to 3000 Volts depending on the power supplied to the locomotive as different countries have different standards for railway electrification. A relay shuts off the system if voltage spikes above 3900V. The power flows through a manual main switch and a main fuse to a voltage selector, which directs it to three resistor-packs depending on which voltage is detected. Power then goes to a heating safety switch (“Heizschütz”), which provides both power to the pump and to the heating coils. The heating safety switch (HSS from here) is designed to shut off the heating coils if the water exceeds 95°C.
The investigators had the burned out Am208 towed to a maintenance facility at Berlin Grunewald station along with an intact one , where the train cars were examined on the 17th of December 2019 by experts from the TÜV Süd Rail and BEU investigators (the BEU is the entity in charge of investigating rail accidents in Germany). Officers from the federal police were also present, along with the CEO of the Centralbahn. The investigation noted several anomalies during the dissection of the heating system on the burned train car:
- The heat exchanger was almost completely dry
- The HSS, a physically movable switch, was stuck. The report likens to it being “glued”, damage usually linked to excessive voltage.
- Electric burn marks on the back of the high-voltage equipment box holding the HSS and the resistors
- Traces of electrical arcing on the case of the main fuse
The investigation followed the evidence down the path of a voltage spike at some point before the fire, which damaged a possibly worn HSS-module, effectively welding it in place. When exactly this had occurred couldn’t be determined, in part due to the train car not being in daily service, but the Centralbahn’s failure to provide any paperwork proving a regular inspection of the system makes it possible that this condition had existed for a considerable time. The train car was operating with a valid inspection certificate and had evidently been maintained in accordance with the requirements for these inspections. What exactly had been done to make it pass each inspection wasn’t fully documented though, and the heating system itself wasn’t part of the mandatory inspections anyway.
Several passengers reported that the interior of the train car had felt “extremely warm”, but nobody had thought that this was a problem, often tracing it to the train just being very crowded. What had really happened was that the stuck HSS caused the heating system of the train car to be permanently turned on, heating the water in the pipes past 100°C and thus also excessively heating the interior of the train car. The increasing temperature caused the water to evaporate in large quantities, which was likely the supposed smoke spotted by the dispatcher at the station. The evaporating water caused the concentration of antifreeze in the system to rapidly increase before it, too, began to evaporate, creating flammable gasses.
The investigation did agree with the Centralbahn on the fire not starting in the heating-system below the train’s floor, but they found the cause to be just a short distance away in the piping towards the overflow tank, which is located in the roof of the car. However, the gasses couldn’t ignite within the heating system, no matter how hot the tubes got, as there was no oxygen in the tubes. Several experiments also failed to ignite different materials from the train car’s interior purely by bringing them in contact with the hot tubing.
Another examination of the intact “comparison car” finally brought the investigators to the missing puzzle-piece. There was a small viewing-window for the overflow tank, located just below the ceiling of the aisle that ran on one side of the train car and from which the compartments were accessed. This small piece of glass, meant to let train staff see how much water was in the overflow tank, most likely burst from the excessive heat of its tube. This allowed the flammable gas to escape the tubing into the interior of the train car. The police secured video footage of the train ahead of the fire during their investigation, which shows some compartments with the lights turned off. These were later turned on as the fans boarded the train. This means that all the lights were turned on between 7:30pm and 8:01pm, and the investigation concluded that one of the light switches created a minor spark which was sufficient to ignite the hot, flammable gases in the roof of the train car. The fire then began to burn between the inner ceiling and outer roof of the car, where it was detected due to the smoke it produced, only “falling through” to the interior below as fans were already evacuating the train car. The train’s heating-system continued to produce steam from evaporating water and antifreeze until the overhead catenary was shut down at 8:11pm as part of emergency procedures.
The TÜV’s expert noted that, by the time it was detected, the fire was past the point where it could be subdued with the onboard fire extinguishers, meaning the only right thing to do was what the driver did, stopping the train at nearest point where passengers could evacuate and then letting the fire department take care of it. It was also noted that the fire could have had far worse consequences later along the train’s journey, mainly based on the theory that increasingly tired (or even sleeping) passengers would have taken longer to notice the smoke and fire.
There had been reports by fans who had traveled with the train car on earlier occasions and felt that it was heated “more than necessary”, but the Centralbahn couldn’t provide any paperwork stating how, if at all, they reacted to the possibility of a faulty heating system. It also wasn’t clear if the driver or conductor knew that the heating system could be shut down with a lever on the outside of the car. Shutting down the heating system when the steam was spotted venting from the car could have allowed the system to cool down somewhat, stopping a further increase in temperatures in the system. The driver also didn’t grow suspicious as to why one train car was emitting steam when 12 others weren’t.
The Centralbahn promised that they would improve both maintenance and staff training regarding the heating systems, which was followed up with the EBA (Eisenbahn Bundesamt, German Federal Railway Authority) banning the usage of water-heated passenger cars which were powered by a high-voltage supply from the locomotive if there was no secondary shutoff mechanism by the 17th of January 2020. Other Am208 thus had to be retrofitted with the high temperature shutoff if they didn’t have one already, or they could no longer run on German rails. None of this affected the burned train car though, as the damage put it well beyond repairability and it was subsequently scrapped.
Adding Insult to Injury
As I probably have some soccer fans among my readers I thought I should point out that Freiburg’s fans had to deal with this entire ordeal after their team lost the soccer game 2:0.
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