 Whenever I think of runaway trains, I for whatever reason imagine it happening in black and white. Like in an old Buster Keaton movie, maybe it's because they really shouldn't be happening in the modern day. I mean I know they do, but with things like train line pipes, spring applied brakes and hell even breakmen of old, they shouldn't really happen. But of course they do and the results are often a little bit crashy. So if I was to tell you that a runaway happened on the London Underground during rush hour, just over 10 years ago, you'd probably be surprised that it didn't end up with a big bang. Well, with the fast actions of controllers, signals, railway topography influenced by 100 year old electric train shortcomings and a little bit of luck, thankfully no one died. Today I'm covering the 2010 Highgate runaway and welcome to Plainly Difficult. A forward. So in my day job I have to look a lot at these little things which are called RAIB reports and in 2016, in a previous job, I was being taught about this particular incident at Ashfield House during a training course. The incident should have been seen a mile off, but I won't spoil it this early on in the video. So as a little note, this video uses the RAIB report for the basis of its facts and figures, so if you like some fair reading then I'd highly recommend checking it out. I'll also be drawing upon some of my real world knowledge of the event and my personal experience from when I actually worked on the railway in question. So, warning, I'm going to get a little bit geeky in this video, but sadly there isn't too much about signalling so you've been lucky this time. A background. Before we get into the comedy of errors, let's have a little bit of background on the Northern Line. The Northern Line is London Underground's oldest deep level tube line. Originally, the line that we know today was actually several different lines with the first section opening in 1890 under the name the City in South London Railway. In 1907, another railway opened called the Charing Cross-Euston and Hampstead Railway. By the 1920s, both lines had stations at Euston and plans were hatched to combine the two to make a north-south route. The formation and connecting works resulted in a line that had two routes through central London. By the mid-1920s, the line was pretty much what we have today, give or take. I do recommend looking at Jago Hazard's videos for the plethora of information on the history behind the Northern Line. But what is important here is the gradients on the lines going north is very much an uphill game, thus going south is very much downhill. You can't really change that part about London, but this could be an issue for early electric trains. However, there are little things that can be done to help the trains, especially when it comes to braking. If your station is at a slightly higher elevation than the line, then you force trains to go uphill before the platform. This slows trains down, and when trains depart, they get a little boost with the help of gravity. I should say this is more noticeable along the modern extension, but at Warren Street, this ramping up to the station is still employed. Now remember this for later. Now I should say the whole ramp up to the station theory I got from my time at Ashwood House, so it may just be an old wives' tale, but there's still a gradient on approach to Warren Street from the southbound road. So the Northern Line's party trick of two routes through London is underpinned by two areas. Kennington, its loop turn back sidings, and crossover, and the absolutely confusing Camden Town Junction. Here, any southbound train can be routed to both southbound branches heading towards Bank and Charing Cross respectively. Anywho, as I mentioned, the line is electrified and this was done in the modern day on the LUL standard 630V 4L DC traction current method. Being in a tunnel means electric powered vehicles is preferred, but how do you move stuff around when the power is off during maintenance? Well, how about battery locomotives? But finally for today's video, we aren't actually going to talk about those. We're going to talk about a type of rail vehicle used on the underground that actually goes in the tunnel with a combustion engine. This was the rail grinding unit. The machine was built in 2001. It grinds a rail profile and it runs off a diesel engine and is self-propelled consisting of two cab cars and a middle carriage. The whole unit weighed roughly 37 tonnes and it was operated by Schwerbau GMBH staff. It's allowed to run in the tunnels providing proper ventilation is in place. The train isn't actually owned by TFL, instead it's rented out to the operator for use for a period of time each year. It was first used in 2002 and found itself grinding all over the underground network, but it wasn't without issue. Don't get me wrong, every train breaks down once in a while, whether it being a traction auxiliary trip in the Hendon tunnel, train line burst on the Bekelu or central line train losing its code. It happens and the rail grinding unit was no different. Now our path to the runaway began not on the northern line, but on the Jubilee line on the 17th of July 2010. The RAIB would uncover this problem post incident, but the rail grinding train would break down and require rescuing. Often assistance is provided from an empty passenger train, but this also brings an issue, couplers. Underground trains have a standard design called the auto coupler which uses a wedge lock, but the rail grinding unit uses its own type of cleavage arrangement and worse still, the two couplers are at different heights. This is where this kind of train sex toy comes into play. This is called the emergency coupler. It connects the two incompatible couplers together. It also has the ability to bridge the height difference as well. So on the Jubilee line issue in July 2010, the unit had broken down and a Jubilee line 96 stock unit was sent to push it from West Hampstead to the depot at Neesden. When the 96 stock train pushed the broken rail grinding unit, the emergency coupler started to bend. Not good. So it was decided to rescue the RGU by hooking up the emergency coupler to the other end and drag it to Neesden. This did work, and in response to the incident, LUO investigated the cause of the coupler deflection. A strengthen coupler would be provided, but it would take a little while to get one made up and sent. So what to do with the rail grinding unit? Well, recovering it by dragging works so well, before, as such LUO and tube lines agreed to just pull it if it failed in the meantime. And we kind of know where this is going to end. But run away. Right time to get out your bingo card. It is the early hours of the 13th of August 2010, and the rail grinding unit is working on the northern line in the archway area. At around 3.30 in the morning, the operators tried to start the engine for the rail grinding unit, but no luck. The train was stopped roughly 500 meters north of archway. On the southbound road. It could be fixed, but it was decided it would take too long, but it to drag it to the safety of high gate sidings and deal with the fault out in the open. Northern line control range for a 95 stock train to come down the south bore, meet and couple up to the failed RGU, and then drag it back in the wrong direction back to east Finchley. Simple, after all the RGU had been pulled out before. With a plan in mind, an empty passenger train was dispatched from East Finchley at around 5.30. On board was the operator and duty manager of trains, the LUL equivalent of a network rail mobile operations manager. Meanwhile, trains on the line began to leave the northern lines many depots and sidings around 5am in readiness for the beginning of traffic. Of course, with the Wuhan, the Barnett branch, the service there was, shall we say, up the wall. Trains come out of Goldersgreen depot, running into 27 Road and then into platforms 2-5, depending on whether they are heading north, or for the driver to change ends on the platform and head south towards Camden. By the time the rail grinding unit was being dragged, a number of underground trains were running south along the Bank and Charing Cross branches respectively. Due to the failed rail grinding unit, no trains could be sent down from East Finchley. The assisting train reached the failure site at roughly quarter to six in the morning, and the RGU crew and train operator set about hooking up the emergency coupler. After the emergency coupler had been deployed, the RGU had its brakes taken off. Something that couldn't be reversed when the unit was in motion, thus the RGU was attached on brakes to the rear of a train heading uphill. The movement started at 6.34, and the two trains slowly crept up the 1 in 60 gradient towards Highgate. Around 10 minutes later, they had passed Highgate, but around 100 meters north of the station, the assisting train experienced an emergency brake application. The coupler broke. In its forward motion, the RGU banged into the rear of the 95-stock train and then started rolling back down south. The crew aboard the RGU, knowing that can't apply the brakes whilst the train was in motion, took the chance and jumped out of the unit as it rolled back through Highgate. This is the pixelated face of someone who's having a bad day. The train was now running free and completely unmanned. Meanwhile, a passenger service, train number 107, had gone into the sidings at Archway and had come out on the southbound, waiting to make up its return working to Morden. Northern Line Control called the driver of the train and told him to depart and head south. He was being chased by a runaway train. Control told him at Toughnell Park to drive fast and to not stop at any stations. Not stopping, although keeping the train moving, isn't a very fast affair as the station starting signals were set to release on approach as long as the train is travelling at 5mph or less. The rulebook for train operation on LUL even states 5mph as a maximum speed when running non-stop through stations. The RGU was gaining speeds up to 35mph. Getting close to Camden, the gap was just 46 seconds between the RGU and train 107. As the track flattened out to approach in Camden, the RGU lost some of its momentum, but it was still rolling. Not knowing the actual distance the runaway would travel, Control and staff had to make a decision on a real life trolley problem, to decide either to run down the bank or cross branches. Which option would potentially kill less people? The cross it would be. Of course, there was more to the cross branch as it had a few places to potentially derail the train, and they had the option of running the train around the Kennington loop or into the Kennington sidings to smash into the buffer stops. Either of these options could result in the RGU derailing or crashing. A tough decision, especially when the controllers weren't aware that the crewable with the runaway had actually previously jumped off. Train number 107 had a very close shave and thankfully was diverted down the bank branch. So at 650, the RGU was now on the chairing cross branch and travelling at around 12 miles an hour. Controllers tried to derail the train at Mornington Crescent, but it smashed through the points and carried on south. Finally, on the approach to Warren Street, the train was slowed on the uphill gradient, and was stopped at 6.58 in the morning. A totaled runaway had lasted 16 minutes and travelled around 4.3 miles or 6.9 kilometers. Luckily, no one was injured, apart from the two crew members on the RGU who had minor injuries from jumping off at Highgate. Although this result could have been far worse if luck wasn't on the side of LUL that morning. The RGU would be successfully recovered and the point work at Mornington Crescent would be fixed overnight. But how is the situation allowed to happen? Well, this would bring in the RAIB and their investigation. Enter the RAIB. In the UK, if there's a bulls up on a railway, then the RAIB gets involved, and of course a runaway train in rush hour on one of the busiest railways in the UK would peak their interest. Clearly, the broken coupler was the cause and dragging rather than pushing or boxing in the fell train, i.e. having a train either end. But why did the coupler brake at Highgate? Well, the RAIB found that before the breakaway, the 95-stock train experienced an emergency brake application. You see the train was working in a restricted manual mode. This limited the train's speed to below 10.6mph. It's used today for the RM whole procedure, but pre-automatic operation, restricted manual was used after a train was allowed to pass a signal at danger, thus restricting the train to a speed that's likely to stop short of any obstruction until the train had passed two consecutive stop signals showing a proceed aspect. But the system was set up that it would give the operator an alarm if the speed approached 10.6mph from above 8mph. The alarm could be cancelled and will reset if the train goes below 7.5mph and starts to creep above 8mph. If the speed went over 10.6mph, an emergency brake application would be applied. So why the emergency brake then? Well, the operator received an alarm multiple times, as keeping such a low speed on an uphill gradient is tough. This resulted in 60 times the operator taking power and then stopping power in the 8 minutes and 10 seconds before the breakaway. It was seen that the train's operator had acknowledged the alarm, but the train's speed hadn't gone below 7.5mph and thus when again approaching the maximum speed in restricted manual mode, the train applied the brakes without the audible alarm. This was enough to initiate the coupler brake, thus starting the runaway. Now the overall issue is that the procedure for pulling the failed train wasn't really set out. The RAIB uncovered that no one on site had an official procedure for an unbraked train. Some assumptions were held that the two trains would be connected by chains as a secondary coupling, but this wasn't communicated to those on site. Basically it would seem everyone that day was just winging it, which unfortunately is more common than you may realise. The RAIB would summarise the underlying factors. I'd like to say thank you for Chloe for reading it out for me. As reported by the BBC, London Underground, LUL, TubeLinesLimited and Schwerbaugh, GMBH pled guilty at the Old Bailey to endangering passengers and staff. They were each fined £100,000 for a total of £300,000. And that was the story of the runaway train on the underground. Now disaster scale time. I've redone it and it's now in its version 3.0 form. It rates on death toll, so being a death-free incident is going to be a one, because there wasn't really any damage apart from some smashed up point work and probably some brown trousers of those involved. This is Plainly Differt Production. All videos on the channel are created with comments that you should share like licence. Plainly Differt videos produced by me, John, in the currently wet and windy corner of Southern London, UK. I have a second YouTube channel, Instagram and Twitter or X, so check them out for other random bits and pieces that I do. And I also have Patreon and YouTube members. 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