#br711

Source: Falk2 on Wikimedia commons, CC-BY-SA

This is the class 711.1 overhead line maintenance car, one of several different types of similar vehicles. It is designed to fix any problems that may develop with the overhead lines. It's diesel-powered, obviously, and it has a big workshop on the inside full of all sorts of copper equipment, and on the top, a special pantograph for checking wire alignment and a working platform from where you can actually touch and work on the wires.

The official nickname for them when they were introduced was Hubarbeitsbühnen-Instandhaltungsfahrzeug für Oberleitungsanlagen (lift working platform maintenance vehicle for overhead line equipment), or in short HIOB, the german spelling of the biblical Job, which was definitely not a bad omen at all.

22 of these were built between 2002 and 2004, and they (as well as other similar vehicles) are stationed all over Germany to react quickly to any issues with overhead lines, as well as do various forms of regular checks and maintenance. The 711.1 is special, though: It keeps catching on fire.

Picture by fire brigade Bienenbüttel, found at https://www.az-online.de/uelzen/bienenbuettel/flammen-bahn-1605363.html

The first one burned down in 2012. Nobody got hurt (in any of the following incidents), and it was treated like a freak accident. Specifically, the investigation revealed that it's related to how the train functions. Normally, for a diesel train, you either have a direct mechanical connection from the motor to the driven wheels (sometimes including something like the torque converter in an automatic gearbox), or sometimes the diesel engine drives an electric generator and electric motors at the wheels drive the train. This, on the other hand, has a hydrostatic transmission: The main engine drives a pump that creates pressure in an oil system, and this high-pressure oil is then used in motors at the wheels to drive the train.

The good thing about this arrangement is that the train can run both fast (up to 160 km/h or 100 mph) to quickly reach the place where it's needed, but also really slowly, walking pace or slower, so someone standing on the roof working platform can check every part of the wires carefully.

The bad thing about this arrangement is that the oil in the system is flammable. If there's a leak, it sprays out, and if that spray hits something hot, it can ignite. That's what happened here. Okay, gotta do better maintenance, alright.

Then it happened again, in July 2020.

Source: German Federal Police, via official accident investigation report

The cause was pretty much the same, but the effect was much more noticeable. The train was underway on a training run when it came to a stop for no clear reason. The staff activated the parking brake, got out, and noticed that their train was on fire. As they were calling firefighters, however, the train suddenly started to move. The engineer actually climbed back on board and tried to activate every braking system the train had, and it had a lot of them; this one was specifically equipped for more mountainous railway lines. But none of it worked, and the engineer jumped back out at still low speeds (no reported injuries).

It kept rolling downhill for 22 kilometres (about 14 miles). Station staff tried to stop it by putting signals on red and hoping for the automatic train control system to stop it, but train control systems can't do anything if there are no brakes. Others tried to put wheel chocks on the rails, but those are for parked trains, fast trains will just throw them to the say. So on it went, burning more and more. In the end the railway decided to find a nice save spot where nothing important was around and firefighters would have easy access, and let it derail there. That's what the picture above shows.

What happened? Well, the same as before, but this time with an additional twist. The fire had destroyed all normal braking systems. It hadn't destroyed the parking brake, but on this train, the parking brake is electrically controlled. You don't need to electricity for it to stay active, but you need it to activate or deactivate it. The fire had already destroyed the relevant electrical lines when the engineer thought they activated the parking brake.

Two trains of the same type burning down for the same reason is scary and warrants action, even if it's eight years apart, and the accident investigation report lists a number of steps already taken and others that were planned, like more checks for leaks, new procedures for leaving the train so it doesn't roll away, perhaps changing some equipment out.

And it seems to me personally that these changes had an effect. Of sorts.

You can ignore the narration (which consistently calls it an engine even though it's a rail car), just admire these pictures of a driverless burning train coming towards you. Yes, in January 2023, another of these trains caught fire, it rolled away again, and got derailed on purpose again. We don't have an official accident investigation report yet, so who knows what happened here, but, like, it's not exactly hard to make a guess.

Just to really hammer the point home, let's go to February 2023, just a month later, and this time we see the same thing in Dresden.

Picture: Credited to "Firefighters", from https://bahnblogstelle.com/198726/erneut-brand-von-instandhaltungsfahrzeug-diesmal-in-dresden/

This time it didn't run away! My understanding is that the train drivers, well aware of the history of this type, placed wheel chocks in front of the wheels before it had the chance to do anything crazy.

Which brings us to last month. You won't believe what happened June 13th, 2024:

Picture: Firefighters Haan, via https://rp-online.de/nrw/staedte/haan/triebwagen-brennt-auf-der-bahnstrecke-gruiten-hochdahl_aid-114420335

So as the Wikipedia infobox helpfully says,

that's five out of 22 burned down. I gotta say, if your train's Wikipedia article has a "train burned down" counter and a section of fires that's nearly a third of the whole article, that's an issue.

(Ironically, it is actually not the most-burned-down german train by percentage. That dubious honour goes to the MaK DE 1024, an experimental heavy diesel locomotive. Three were built, two of them burned down eventually. The sole survivor was, in the numbering scheme of its last and longest owner, number 13.)

As of right now, DB has decided that these trains can't be trusted with engines, so for now they will all have to be pulled by locomotives. To me that sounds like it should fix the issue, for some value of "fix".

It's definitely notable that during the first 18 years of this type's use, they suffered two fires, and after they implemented all sorts of fixes after the second, three more burned down in just four years. I don't want to say the fixes made it worse, maybe it's just age starting to show, but it doesn't seem to have helped any.