 When you think of railways, the first thing that usually pops into mind is trains. Understandable as it's the thing you climb aboard whether it's on a day trip, overnight sleeper or the dreaded sweaty commuter service. But a railway is more than just its vehicles. True they are often the draw for passengers, however they are just one part of the greater machine. The rails are pretty important. Well it is in its name. They are the unsung heroes and their healthy condition can never be understated. Today's video is about the rails and the highly complex parts around point work. Welcome to Plainly Difficult and in this video we're looking at the Potter's Bar rail disaster. Background. So I'm going to divide this video's context filling in section into two parts. One a brief history of Potter's Bar train station and another on the geeky side of point work. My main research material came in the form for this video from the HSC report and the RSSB investigation into the disaster and as always the linkies will be in the description below. I'll also link in some other bits and pieces as we go along such as newspaper articles. Oh and also I'll be drawing on my experience in the rail industry as well. Now you don't get an image like this from a good day at the office. I should say this is probably the first picture I've ever actually seen of Potter's Bar train station. Any who catastrophe aside the town of Potter's Bar has a railway station. It's roughly 12 miles and 57 chains from London and is in the county of Hertfordshire, which is around here on the map. As a side note a chain is a measurement of distance and there are 80 to a mile and on the railway we still use chains for some reason as well as kilometres, feet, yards and meters. Just because well the UK is a messed up measurement living nightmare. I like to call it Empyrametric. The station opened in its first form in 1850 and saw changes to its buildings and platforms over the years. Its final layout had two 160 meter long 11 meter wide island platforms, which were partially covered by reinforced concrete canopies which were installed in the 1950s. The station serves stopping services but also is part of the East Coast mainline as such trains go fast through the station. The track layout was down slow for stopping services, down fast for non-stopping trains and up fast and up slow. And down in our case today means away from London and up is towards London. The line speed is 115 miles an hour at least it was in 2002 and to allow trains to change lines there are points at the southern London end of the station. This allows down fast trains to cross over onto the slow lines and for up fast and slow services to change tracks. The layout also allowed a train to come into Potters Bar on the down slow, terminate, allow for the driver to change ends and then head back towards London on the fast or slow lines. Regardless all we really need to know is that there are points here and it's pretty common across many stations in the United Kingdom as it affords flexibility in what services trains can run. In particular at Potters Bar the points normal position was set for straight through running. From the perspective of track maintenance the point work south of Potters Bar was designated a red zone i.e working on the area brought in the risks of train movements and would likely need a line block in layman's terms to stop all trains in the area in order to inspect or maintain the infrastructure. The term red zone is no longer used in the current rulebook however when this disaster happened which was 2002 it was. So needless to say having the points in this area adds some agro to maintenance work on site. Well we've always chatted about point work let's have a look eh? So points or switches as are known in some other places in the world allow trains to change lines. They are vital in enabling multiple trains to run on a network as if they didn't exist then trains would just be locked into one particular track and just go up and down. Points are simple but ingenious they are made of several very important components. First of all there are the stock rails and these are fixed. Then you have to switch rails or blades. These can move and depending on the intended direction allow the wheel to run along it. You see that the train wheel flanges are like this and thus they need to be able to cross the rail. This is done here with the actual crossing section basically an interruption of the railhead to allow the wheel to slip through. Finally once the wheels have moved over the points they go through a thing called a check rail that makes sure the wheel is in the correct position. So with the blades moving there is a risk that they can go out of gauge i.e. too wide or too narrow for the wheels distance between each other. In the UK the standard gauge is used which is four foot eight and a half inches wide. This holding of gauge is done by things called stretcher bars. These can be adjusted as they have threaded ends which pass through a support bracket in which a nut each side is threaded on. The bracket is then attached to the switch rail and the points machine was attached to the points via a lock stretcher bar. Now today's story will be mainly about this set of points to the south of Potter's Bar numbered 2182. Needless to say maintenance is key for their safe operation as being on the fast lines they take quite a beating from very heavy and quick moving trains. Now the area is remotely controlled by the King's Cross signal box and a line is electrified with overhead lines of 25 kilovolts of AC. So that was a basic background let's have a little advert break. Great to see you back so I need to quickly mention something that is rather important to our story and that is of a rough ride. Now it's not what your dirty mind is thinking of, it's actually an event of a train passing over a section of track and for whatever reason is bounced around causing the feeling of a train to be not stable or rough ride as you will. Many things can cause this a rolling ballast track out of gauge rails, a train's wheels hunting around corners, broken fish plates, loads of things really but also a rough ride can be caused by faulty point work. How the exact location of a rough ride is pinpointed really depends on who reports it for example if it's a driver then they can get a mile post number a stanchion number signal number or even nearest junction name the list is very exhaustive. Such events are easily zeroed in on but it's much more difficult if a passenger reports it because well they might just say it happened between X and Y station making a search area of miles of track rather than just a few yards but regardless of how a rough ride is reported the way it's investigated is usually the same a train will be held at a red signal before the affected area after which the signaler will inform the driver of a rough ride and to proceed at caution over the affected area when at a pre-agreed location the driver is then to contact the signaler and report their findings this type of house of course working is fairly regular depending on what the driver says another few more trains can also inspect the area and if a problem is found then track workers are sent to the site and now we can start with our disaster narrative so get your bingo cards at the ready the disaster so our story begins the evening before the crash on the 9th of May 2002 a station announcer is traveling home from finsbury park to his home in stevenage this is at around 9 p.m in the evening as a train is traveling towards potters bar actually i'll tell you in the person's own words has written in page 61 of the rssb final report the train dipped to the left hand side it then seemed to jolt downwards then as it passed over the down faster down slow points it dipped to the left as it traveled across the bridge over dark slain the train lifted and lent to the left passed over the bridge and then lent back to the right as it came off the bridge when the staff member got to stevenage he reported the rough ride the station supervisor then reported it further up the chain of command to the signal some confusion came around as to who had reported the rough ride and as to what line and points it had occurred on as somewhere along the communications chain the report of a rough ride was taken to be on the up fast service rather than actually on the downfall service nevertheless a rail track member of staff went down to investigate he was looking at the points on the up fast shining his torch over the stretcher bars and their support brackets and associated bolts and nuts and all looked good the member of staff informed the signal box all looked good and well but he would wait to observe the next up fast service travel over the points everything was fine and as such the report went no further however he had been looking at the wrong points it is just after lunch on the 10th of May 2002 and train to papa to six is departing kings cross the 1234 service was set to run along the fast line and cross onto the slow at potter's bar this was to allow a fast service to overtake it this was the 1245 kings cross to kings lin train with the headcode of one tango six zero the stopping service navigated the points and the signal at kings cross saw no issues with setting the route and resetting the points to 182 back to their normal through running position all the required route set lights were showing on the signalers panel now the fast service was operated by west anglia great northern and was a four car class 365 unit capable of a top speed of 100 miles an hour it had departed kings cross on time and along its journey the train was happily climbing up to its top speed as train one tango six zero approached potter's bar the driver noticed the signal on the downslow just outside the station changed from green to red and then back to green again as the front of the train reached the platform at potter's bar the driver noticed a strange jolt followed by more severe jolts the driver took the power off all of a sudden his line light extinguished and the train began to give alarms normally when the line line goes out it means you've got no juice i electricity and this was the case well kind of actually what had happened was that the train had separated but a driver didn't know this until the train came up in a heap so as the train had gone over the set of points the first two carriages and first bogey of the third had successfully made his cross the rear bogey of the third carriage had become derailed and the rear bogey of the fourth carriage derailed and then re-railed onto the crossover pushing it broadside to the direction of travel the fourth carriage became detached from the rest of the formation and running at an angle to the track direction flipped and crashed into the platform at potter's bar becoming lodged at a 45 degree angle underneath the canopy resulting in this during the flip the bridge over dark slain was smashed into sending debris and masonry smashing into the road below in doing so striking passerby agnes quinn liven killing her so by now the three remaining carriages had come to a stop the sigler noticed several sections becoming occupied on his panel this along with point work showing out of alignment and it prompted the signal to replace all down signals in the area to danger a rail track production supervisor at potter's bar called the signal informing them that a major accident had occurred soon enough it was apparent that six people aboard the rear carriage of the train had died and in addition of agnes quinn liven the death toll as reported by the guardian newspaper medic said five people had died at the scene and two further people died later in hospital hurt for cheer and bed for cheer ambulance services said a further 15 people had serious injuries some of these are now said to be critical a local gpss 70 walking wounded now there was one hell of a mess to be cleared up and leaders to say the cause had to be found out and this leads us up to the next section of the video aftermath and investigation the health and safety executive set up an investigation board and along with rail track her majesties rail inspectorate the british transport police and the rssb looked into the immediate and underlying causes of the derailment now the report of a rough ride was more than a coincidence and when investigators looked over the crash site it was clear to see that the points had played a part the physical evidence allowed the hsc to reconstruct events alongside the trains on board data recorder clearly the points were the cause of the derailment but why well two theories would be thrown out so let's start with the least credible i should prefix this theory with don't forget this is 2002 and terrorism was on a lot of people's minds so the engineering company in charge of maintenance of the point work in the area called jarvis rail would push out the theory of sabotage yes rather bizarre i know and it was easily refutable with the evidence at the crash scene and especially when investigators looked at other jarvis rail maintain point work other issues shall we say could be seen in their maintenance schedules you see interestingly during the investigation the points in question had actually had some maintenance work undertaken on them by jarvis rail on the 1st of may just a few days before and during interviews with jarvis staff it became clear that many didn't really understand the type of adjustable stretcher bars used on the points in the rssb final report they would say the lack of a training program was a result of the failure to produce a procedure for the installation of adjustable stretcher bar assemblies despite the stated intention in 1993 to do so ah so maybe sabotage was not the cause then maybe jarvis rail was undertaking a little case of deflection this leads us on to the second and more likely cause in that the point stretcher assemblies were not properly tightened thus allowing them to gradually become loose and interfere with the running of trains it was also found that vibrations from passing trains could cause the stretcher bars nuts to work themselves free the poor maintenance sadly could have been discovered when the rough ride was reported but the breakdown in communication between the reporting staff member the signal and track worker meant that the wrong set of points was investigated the hsc would summarize this point there appears at this stage to have been a failure to recognize safety related defects in the set up and condition of points 2182a and to record or report them there were deficiencies in the response to a report of a rough ride in the area of the points south of potters bar station on the night before the derailment occurred the 9th of may 2002 thank you mr jago so the disaster was really just down to common issues unpreparedness of managers and staff to maintain and highlight issues within complex machinery sadly this resulted in seven deaths not only that but it became the nail in the coffin for a rather controversial private company rail track which was in charge of maintenance of signaling track and most of the uk stations in a post uk railway privatization world you see rail track had subbed out nearly every job it could to contractors which resulted in substandard infrastructure as you know running a rail networks assets for profit doesn't always get great results by the time the potters bar disaster had happened rail track was actually in administration and a new publicly owned company called network rail was to rise after the ashes now the fines network rail got hit with a 3 million pound penalty a few years after the crash in 2010 jarvis rail who originally posited that sabotage theory ended up emitting liability setting aside 3 million pounds itself for claims against the company network rail moved towards reducing its contractor usage however we've seen more contractor staff in the railway recently which may be a worrying sign the disaster marked a low point in a bloody few years in the uk railway industry but has become less well known compared to labric grove and southall but to me it is actually even more scary as the disaster didn't come from a driver error but a fundamental problem with maintenance now disaster scale time is going to be a four for me and i've got this for my bingo card do you agree this is a plainly for production all videos on the channel are created commons attribution share like licensed plainly for videos which is by me john in a currently very very cold corner of southern london uk i have a second youtube channel instagram and twitter or if you want to call it x so check that out for other bits and pieces i get up to and i'd like to say a very warm thank you to my patreon and youtube members for your financial support as well as the recipe for tuning in every week to watch these videos and all that's left to say is thank you for watching and mr music play us out please