Background
Bad Aibling is a city of 19056 people (as of December 2019) located in the very south of Germany, 48km/29.8mi southeast of Munich and 7km/4.4mi west of Rosenheim (both distances measured in linear distance) near the Austrian border.
The city has no airport, long distance travel is done through the Autobahn 8 running south of the city or via railway. Allowing the latter is a station on the Mangfall Valley Railway (“Mangfallbahn”), an electrified single-track main line running 37km/23mi from Holzkirchen south of Munich to Rosenheim. Opened in 1857 the line was initially mainly used to transport coal to Munich, today it’s exclusively used for regional passenger trains. The whole railway is operated in automatic block sections, if a train occupies a certain part of the track signals automatically adjust to keep following or oncoming trains at a safe distance. This extends to trains being unable to leave a station (due to red signals) if they are meant to wait for an oncoming train. As it’s standard for single-track railways oncoming trains usually pass one another at the stations, due to everything being run with the same model of train overtaking a train in the same direction is extremely rare. The signal-system knows what trains are used for which connection, and sensors in the track count the axles to verify that a train has passed a certain point. Getting it’s name from the Mangfall, a small river, most of the distance is spent running parallel to both the Mangfall and the Mangfallkanal (“Mangfall Channel”).
The trains involved
While the stations and track itself are property of and operated by the DB (German national railway) the operation of the services on the line was taken over by the BOB (“Bayrische Oberlandbahn”) under their “Meridian”-brand in 2013. Using a distinct blue-gray-yellow livery for their multiple units the brand’s trains are easy to tell apart from the red DB-trains.
Travelling eastbound from Munich via Holzkirchen towards Rosenheim was DPN 7905, provided by a six-part third generation “Flirt” multiple unit coded ET 325. Made by Swiss train manufacturer “Stadler” the “Flirt” is a successful electric passenger multiple unit (with diesel- and hybrid versions offered also) mostly for regional passenger traffic, with over 1700 units being made since 2004 for railways in over a dozen countries including Germany, Switzerland, Great Britain and the USA. Introduced into service with Meridian in December 2013 the ET325 measures 107m/351ft in length and can carry 333 passengers (seated) in a two-class configuration, with space for up to 365 additional standing passengers. Weighting 179 metric tons empty the trains can reach 160kph/99mph, enough for their intended purpose. The trains are constructed to comply with the newest safety-norms, featuring special energy-absorbing elements below/in front of the driver’s cabin ensuring sufficient survival space at up to 36kph/22mph. The shape of the forward frame is also designed to keep one train from “mounting” the other’s frame in an accident, a common cause for severe damage to trains and passengers in collisions. Furthermore the cars are connected by special energy-absorbing joints, reducing the forces of cars hitting one-another in an accident.
Coming the other way on it’s journey from Rosenheim towards Holzkirchen was ET355, also provided by a Stadler Flirt 3. This train was smaller though, only being a three-part train. Weighting 114 metric tons the capacity is reduced to 158 seats in two classes and space for 226 standing passengers. The top speed remains the same, with the lower weight allowing a slightly faster acceleration especially at low speeds. The trains are identical on the technical side, with the ET355 essentially just missing 3 center cars but having the same safety-equipment. ET325 has a data-logger in each control cabin with the forward-one recording data as the train moves, while ET355 has one data-logger recording data regardless of the train’s direction of travel.
The Accident
On the 9th of February 2016 39 years old Michael P. is working in the signal box at Bad Aibling station, preparing the paths and stops for the day’s trains. He’s been working as a dispatcher for the DB since 1997, Bad Aibling was the first signal box he was trained at. He had also passed mandatory training for unusual situations, including signal failure, in 2010, 2012 and 2014. At 6:38am he sets a section of the path for DPN 79506, the westbound connection provided by ET355. His input sets the points and signals both for the arrival at Kolbermoor station and the departure towards Bad Aibling. The train arrives at 6:40am and is scheduled to stay at Kolbermoor station until 6:45am to wait for the oncoming DPN 79505 (provided by ET325) to pass and clear the single-track section to Bad Aibling.
On the day the ET325 has a 4 minute delay, usually this would mean the westbound train waits a little longer. It’s Shrove Tuesday, no school and few people working. The trains are almost empty, there’s no rush. Only approximately 150 people are on board (the operator later admits they always have to assume a few people ride without buying a ticket), including the two drivers and a driver in training who is riding in the driver’s cab of ET355 to learn the route before driving it on his own.
Since the dispatcher already set the path for ET355 all the way to Bad Aibling ET325 now can’t depart from Bad Aibling station, the single track section is reserved and the signals cannot be turned green. ET355 will be proceeding as scheduled, the system moved the meeting point of the two trains to Bad Aibling station.
The dispatcher suspects a signal failure, an error in the “counter motion protection” (“Gegenfahrschutz”), the system meant to keep opposing trains out of a single track section. Protocol would now require him to check the neighboring block zones to ensure there are no opposing trains. He neglects to do this, immediately jumping to the course of action for cases when there definitely is just a fault in the system. He activates the replacement signal at Bad Aibling station, overriding the order to stop and disabling the auto-stop of running a red signal. ET325 departs the station and proceeds 870m/2855ft to the block-signal at “Bad Aibling Kurpark”, at Kilometer 28.73.
Still suspecting a fault as this signal won’t turn green either the dispatcher clears the train to proceed with the replacement signal here also, again neglecting proper procedures. The lights on the replacement signal turn on at 6:45am, ET325 proceeds past the signal just as ET355 leaves Kolbermoor. The trains are now on collision course, no more signals along the way can stop them. Now the dispatcher realizes what he’s done, and hurries to send out an emergency stop order. The route along the Mangfallkanal goes around a left hand (for the eastbound ET325) bend, due to the dense woods on the inside of the turn the train driver’s can’t see very far ahead. Adding to that problem is the time of year, while the weather is clear it is still dark. In his hurried panic the dispatcher hits the wrong button, his message goes out to surrounding dispatchers instead of trains at 6:46:20am. At the same time the driver’s suddenly face each other as their trains come around the corner. ET355 is travelling westbound at 52kph/32mph, ET325 is coming the other way at 87kph/54mph. Both trains register the driver triggering an emergency stop at 6:46:55. One second later both trains collide head-on at Kilometer 30.29, without having lost any speed. All 3 drivers are killed on impact, the energy-absorbing elements on either train’s nose are utterly outclassed by the violent impact. The anti-climb elements work in some capacity, instead of mounting one-another and crushing the lower train’s interior ET325 is deflected as it starts to climb, tearing the wall off ET355’s forward car almost entirely as it starts to lean to the right, nearly falling over. A total of 11 people die in the collision, 90 are injured (28 of which severely).
Aftermath
A few seconds after the collision another stop-order is sent out from the signal box, this time it reaches the trains. Obviously, it comes too late. Within a minute calls about the collision reach the local dispatch center, the alarm is raised to a catastrophic event immediately. Helping will be difficult, north of the train tracks lies a thick forest unusable for cars, let alone ambulances and trucks, south of the tracks the Mangfall and Mangfallkanal block most access safe for short service roads on either side of the channel. In a short time, almost 800 responders are involved in the rescue-effort. 215 local and 50 federal police officers, 180 firefighters, both volunteers and full time ones, 120 members of the THW (Federal Agency for technical relief) and 200 EMTs and doctors, including the DLRG and the Wasserwacht (“Water guard”), two lifeguard-services who provide boats to ferry material, responders and survivors across the channel. Every possibly available helicopter is also called in to evacuate survivors, 17 helicopters from Germany and Austria eventually ferry survivors back and forth between surrounding hospitals and the site. To save time the alpine rescue service winches survivors up straight from the wreckage, skipping the transport across the channel to a landing site. During the derailment the overhead wire was torn and shorted out, so the whole wreckage lies in darkness making it more difficult for survivors to free themselves and find their way out of the wrecked trains.
The responders inch their way through the wreckage, worried they will harm trapped survivors by using heavy equipment too early or too much. In daylight the true extend of the damage becomes clear, it’s a taxing sight but also eases the work a little bit. Investigators point out the excellent structural rigidity of the trains, on both the doors from the second car back could be opened without issue thanks to little deformation. The forward cars, while severely damaged, both also maintained some rigidity, especially ET355 which did not collapse in on itself despite an entire wall missing and the roof being forced to the side. Towards noon Germany’s federal traffic Minister, Bavaria’s traffic minister and the German prime minister visit the site to express their sadness and condolences and thank the responders, while Chancellor Merkel and Bavaria’s prime minister publish statements of similar content.
At 11:15am the rescue effort is declared finished, immediately the area is declared a crime scene. Both trains, all the debris, the data-loggers and surveillance footage from inside the trains are confiscated, similar action is taken at the signal box already before this point. The dispatcher, employees of the DB and the Meridian and most of the surviving passengers are questioned about the events. A first indicator of the cause comes from a Meridian-employee riding on ET325. He recalls seeing the (unusual) replacement signal light up both at Bad Aibling station and the Kurpark Block Signal.
Various events around ash Wednesday are cancelled, a soccer game in Germany’s highest league starts with a minute of silence and both teams wearing black armbands as a sign of mourning. A couple of candles and flowers are placed at the site, while a statue in Bad Aibling is covered in a sea of candles the day after the accident.
On the 12th of February, 3 days after the accident, the trains are removed from the scene with the help of two heavy-duty railroad cranes. Four cars out of ET 325 and one car out of ET 355 were able to roll and could be towed away. Regardless, both trains are eventually scrapped in their entirety.
On the fourteenth of February an ecumenical memorial service is hosted at the St. Georg Church in Bad Aibling, attended by responders, survivors, relatives and politicians. The service is shown on a big screen in a nearby gym for locals and also airs on TV. Two days later a charity ice hockey game is hosted in the city, collecting money for survivors and relatives.
With the signaling-system working flawlessly (further calling the use of replacement signals into question) pressure mounts on the dispatcher, who eventually admits that he might have not paid proper attention while working the morning of the accident. Facing a criminal investigation on charges of dangerous interference with rail traffic, negligent manslaughter and negligent cause of bodily injury the dispatcher is arrested on the 12th of April 2016, a day later a severely injured 46 years old survivor succumbs to his injuries and raises the final death toll to 12. At this point it is assumed that he randomly failed to follow proper procedures, maybe due to the early time of day. He causes a public outcry when it becomes known that he wasn’t “just distracted” but had been breaking company policy by using his private phone on duty, playing a game called “Dungeon Hunter 5”. He admits that he had a high interest in the game and might have rushed procedures to quickly return to his game. Investigators contact the Romanian developer and receive stored data from the dispatcher’s account. The data shows that usage of the game on the dispatcher’s phone and rapidly increased since January, spending hours playing the game. The developer also provides chat logs showing the dispatcher actively chatting to other players approximately 12 minutes before the collision. All in all, in the time between 6:09am and 6:41am the dispatcher spent 72% of his time on the game while being on duty. This makes a distraction combined with a subconscious desire to quickly get “interruptions” dealt with very likely. After experts from the Braunschweig University are consulted on the matter this theory is supported, extending to his obsession with the game likely being to blame for him getting the emergency call wrong. Recalculating the timeline it is found that, had he deployed the emergency call immediately and properly, the collision could have been avoided. The report later recommends simplifying the system to get one button sending the emergency call to both trains and dispatchers, but this does not excuse the error.
The city of Bad Aibling plans a public celebration of the responders, it is cancelled on short notice when both THW, the fire departments and the Red Cross express that many of their employees are still very traumatized by the events and would rather not have to appear in public in that way. An official memorial is unveiled in early October 2016, about 1km/3300ft from the site of the accident, on the eastern edge of Bad Aibling. At the site itself small groups of flowers and candles serve as a makeshift memorial.
On the 11th of November the trial against the dispatcher starts, he mostly communicates through his lawyers but does accept that he made mistakes, including playing the mobile game on duty. After six days of trial even his defense admits that there was no doubt in his guilt, although they see a probation to be sufficient. Instead, in December of 2016, he is sentenced to three and a half years in jail, being found guilty on all charges. He is released in July of 2018, having served 2/3 of the sentence, when the remaining time is turned into probation.
The BOB fills the gap left by the destroyed trains with various rented material, in January 2017 Stadler and the BOB agree on an order for two new trains. Since the “Flirt”-model has moved on to a new generation their trains are made specifically. The cost is undisclosed, but claimed to be a sum in the “two digit millions”. The new units arrive in January 2018, re-completing the 35 train fleet, and are in service since. Excluding the cost for the new trains the report lists a damage valued at 20 million Euros/24.2 million USD.
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