73s at EAB

As you may be aware, over the Christmas period there have been major engineering works taking place at Earl's Court on the District line. Earl's Court is a major junction and an extremely important location, with multiple routes converging there. The tube map doesn't quite do it justice, but even so it's easy to see that things get pretty interesting there. Consequently, this work ultimately resulted in a part closure of a large chunk of the District line: there was no service between Edgware Road/South Kensington and Ealing Broadway/Kensington (Olympia)/Richmond/Wimbledon. Or, in other words, everything west of South Kensington was shut down, including the whole of the "wimbleware" (the Wimbledon-Edgware Road branch of the District line). The Circle line, however, was running as normal (service disruption notwithstanding) and so were the Piccadilly line and the relevant bits of the London Overground. This means that most District line stations did actually have a service of some kind.

The reason for this shut down was obviously that no trains could pass through Earl's Court from the east end of the line (South Kensington is the last point east of Earl's Court at which trains can be reversed, I believe, which is why it was chosen.) As it happens, the District line does have a depot at Ealing Common and I, myself, am a tad surprised that it wasn't decided to run a skeleton service - say between Ealing Broadway/Richmond and Hammersmith. I, however, am but a mere commuter and have no knowledge of the whys and wherefores - I just get on 'em :P As it happens, we ended up with something much more exciting than that as a result of all this.

A quick look at the tube map will show you that the District and Piccadilly lines track pretty much the same course (and have many stations in common) between South Kensington and Ealing Common. The reality is that, east of Barons Court, the Piccadilly line descends into its tube tunnels and heads onto Earl's Court, to its own underground platforms. Meanwhile, the District carries on up to West Kensington, before taking its own, generally overground, route to its own overground platforms at Earl's Court. East of Earl's Court, the Picc carries on in its tube tunnel all the way up to South Kensington and on towards Cockfosters. Meanwhile, the District also heads through tunnels to South Kensington; but these are cut and cover tunnels, built much closer to the surface and with numerous short uncovered sections. From South Kensington, of course, the District makes its way up via Tower Hill and on towards Upminster.

It's west of Barons Court, though, which really interests me. I've had a crack at explaining what goes on here before, but this time, I have diagrams! :P So, between Barons Court and Acton Town, there is four track running, with the District line serving the two outer "local line" tracks and the Piccadilly line serving the two inner "fast" tracks. Trains on the local line (i.e. District line trains) stop at all stations: Barons Court, Hammersmith (Piccadilly and District lines), Ravenscourt Park, Stamford Brook, Turnham Green (at all times of day), Chiswick Park and Acton Town. However, trains on the fast line (i.e. Piccadilly line trains) miss out the stations in bold above (and Turnham Green for most of the day). Here's what happens:

At Acton Town, eastbound trains can be routed onto the local line (usually served by the District) or the fast line (usually served by the Picc). Similarly westbound trains from either line can be routed onto South Ealing or Ealing Common. Trains can also head up the sidings, if they are terminating here. Below there is a diagram showing the track layout of Acton Town and it's one of the most complicated locations I've ever seen. To simplify things for myself (because I just don't have enough footage to be able to do it) I've left off the signals. This diagram may not be perfect, though - I had to hack it together somewhat and the signalling diagrams below (which I based this on) show a more accurate view, but I find them much more complicated (as with all things, it does make more sense if you know how to interpret it, but it's still pretty clear that it's a positive labyrinth :P)

A simplified, schematic diagram of the track layout around Acton Town. Not to scale, relative positions may not be accurate

A more professional signalling diagram of Acton Town, showing depot roads (on the left), the station itself (in the middle) and tracks to the East (on the right). Image provided courtesy of "District Dave" (http://www.districtdave.co.uk/html/acton_town.html)

The second (oh yes, there's two) signalling diagram of Acton Town showing the area to the east of the station. Image provided courtesy of "District Dave" (http://www.districtdave.co.uk/html/acton_town.html)

As you can see, it's quite complicated. The main things to appreciate are:

• Trains from South Ealing and Ealing Common (whether District or Piccadilly line trains) can be routed onto eastbound platform 4 and eastbound platform 3
• Trains from eastbound platform 4 can proceed onto Chiswick Park (on the local line) or onto Turnham Green (on the fast line) via the crossover
• Trains from eastbound platform 3 can only proceed to Turnham Green, however, any train approaching Acton Town on the eastbound can be routed into platform 4 as well as platform 3 (as explained in my first bullet point) so this isn't a huge problem
• Trains on the fast line (from Turnham Green) can be routed into westbound platform 2 and westbound platform 1
•  Trains from westbound platform 1 and westbound platform 2 can be routed onto either Ealing Common or South Ealing
• Trains on the local line (from Chiswick Park) can only proceed into westbound platform 1, however, trains can reach Ealing Common and South Ealing (as explained in my previous bullet point) from here, so this isn't a huge problem

The upshot of this is that any eastbound train can be routed onto the local (in general, District) line, or onto the fast (in general, Piccadilly) line. Furthermore, any westbound train from the local line, or the fast line, can be routed onto South Ealing or Ealing Common.

Okay, the next station east of Acton Town is Chiswick Park:

A diagram showing the track layout around Chiswick Park

A view from westbound platform 1 at Chiswick Park looking west towards Acton Town. (Image courtesy "Sunil060902" (via Wikipedia))

As you can see, Piccadilly line trains (from now on, unless otherwise stated, I will refer to the fast lines as the Piccadilly line, since that's the service pattern almost all the time; likewise I will refer to the local lines as the District line) do not stop here - there are no platforms for them to stop at.

After Chiswick Park, both the District line and the Piccadilly line reach Turnham Green:

A diagram showing the track layout around Turnham Green

A view from eastbound platform 4 at Turnham Green looking west towards Chiswick Park and Acton Town. (Image courtesy "Sunil060902" (via Wikipedia))

As you can see, to the west of Turnham Green, eastbound District line trains from Gunnersbury (ex Richmond) merge with eastbound District line trains from Chiswick Park (ex Ealing Broadway or Acton Town). As is obvious, westbound District line trains can also proceed to Gunnersbury or Chiswick Park. Now, on to the Piccadilly line. Clearly, there're two island platforms (an eastbound platform and a westbound platform) which each split the District and Piccadilly lines in the relevant direction. These platforms are theoretically split in half: the District always stops at the outer platforms, while the Piccadilly serves the inner platforms "until 0650 Mondays to Saturdays, 0745 Sundays and after 2230 every evening". Picc trains may also call at Turnham Green if there're some problems or service disruptions and pressure needs to be relieved on the District line. The reason for this non-stopping is something like this (as I say, I just get on 'em, so I don't know the full story): essentially the reason for the four tracks is, I think, historical. Either way, we've got four tracks, we might as well use them. The "local" stations are sufficiently quiet that the District will do, there's no real risk of overcrowding nor is there the serious demand you get somewhere like Bank. Ultimately, the District line is good enough to serve these stations. The Piccadilly, therefore doesn't really need to stop at them (Chiswick Park is actually the only station with no Piccadilly line platforms and the Picc could stop elsewhere). Furthermore, the Piccadilly line is the express line, built for long, cross-city journeys and such and many people on it will be going down to Heathrow (or all the way up to Uxbridge for that matter) and they have a long journey and need to get a move on. In short, the District is all the local stations need, whereas the Picc really needs to get on to Acton Town, which is why it misses out stations. At Turnham Green, there're platforms in both directions, so here is somewhere it could stop. It doesn't for most of the day, for the reasons above, but at other times of the day, I imagine it stops at Turnham Green to supplement the District line service. Also, with the peaks over, the immediate need to get Piccadilly line passengers on their way is reduced. This is the quiet time of day, therefore the Picc might as well stop at Turnham Green. Turnham Green in particular (rather than any other station where it could stop) is stopped at because it's a very useful interchange for the Richmond branch and also because it sees a fair number of passengers. Consultations are, in fact, taking place to explore the possibility of stopping more (or all) Piccadilly line trains at Turnham Green.

Now, on to Stamford Brook, where we have an interesting arrangement:

A diagram showing the track layout around Stamford Brook

A view from eastbound platform 3 at Stamford Brook looking west towards Turnham Green (just visible in the background). (Image courtesy "Sunil060902" (via Wikipedia))

As you can see, there is no platform on the eastbound Piccadilly line, but there is one on the westbound Picc. This, however, is not used, except perhaps very rarely. The District line, meanwhile, uses the outer platforms (1 and 3).

Finally, at Ravenscourt Park, we have the same arrangement as at Turnham Green:

A diagram showing the track layout around Ravenscourt Park

A view from eastbound platform 4 at Ravenscourt Park looking west towards Stamford Brook and Turnham Green. (Image courtesy "Sunil060902" (via Wikipedia))

The Piccadilly line platforms, in this case, however, are extremely rarely used. They may see some use during service disruption and engineering work, but otherwise they aren't used. There have been calls, most notably by London Assembly member Murad Qureshi, to have the Picc call here regularly, but I doubt they will be answered.

Finally, we have Hammersmith and Barons Court, which really have to be treated together:

A diagram showing the track layout from Barons Court to Hammersmith

It's no Acton Town, but - as you can see - it's quite complicated. The "take home message" though is this:

• Eastbound trains from Ravenscourt Park on the local line arrive at Hammersmith's eastbound platform 4, from where they can proceed onto eastbound platform 4 at Barons Court and from there to West Kensington (on the District line) or onto eastbound platform 3 at Barons court and from there onto Earl's Court (on the Piccadilly line). Because of the width of the tunnels, only Piccadilly line trains can do the latter and I doubt they ever do the former either
• Eastbound trains from Turnham Green on the fast line arrive at Hammersmith's eastbound platform 3, from where they can proceed onto eastbound platform 4 at Barons Court and from there to West Kensington (on the District line) or onto eastbound platform 3 at Barons court and from there onto Earl's Court (on the Piccadilly line)
• Westbound trains from West Kensington on the District line arrive at Barons Court's westbound platform 1, from where they can proceed onto westbound platform 1 at Hammersmith and from there to Ravenscourt Park (on the local line) or onto westbound platform 2 at Hammersmith and from there onto Turnham Green (on the fast line)
• Westbound trains from Earl's Court on the Piccadilly line arrive at Barons Court's westbound platform 2, from where they can proceed onto westbound platform 1 at Hammersmith and from there to Ravenscourt Park (on the local line) or onto westbound platform 2 at Hammersmith and from there onto Turnham Green (on the fast line)

Or, in short, eastbound trains from both the fast lines and the local lines can be routed into the District line platforms at Barons Court (and continue to West Kensington and off along the District) or the Piccadilly line platforms there (and continue to Earl's Court and off along the Picc). In the other direction, westbound trains from Earl's Court and West Kensington can be routed onto the local line (the District) or the fast line (the Picc) and, from there, they proceed to Acton Town (stopping, or not, at the intermediate stations) and on to their final destination (or up a siding, of course, if they're terminating at Acton Town). Trains can also terminate at Hammersmith and run up the siding.

Phew. So, the upshot of all that is this: Both District and Piccadilly line trains can use both the fast (not stopping at any stations (except Turnham Green at some times)) and the local (stopping at all stations) lines between Hammersmith and Acton Town. The usual pattern, though, is perfectly represented by the tube map, with the Picc using the fast and the District the local.

So, why am I telling you all this? Well, partly because I find it interesting, but mostly because on Sunday (when I went on a trip to sample the various unusual workings due to the engineering works at Earl's Court) there was no District line service here at all. As a result, the Piccadilly line trains were being routed onto the local lines, with all Piccadilly line trains serving all stations (except when some occasionally had to be sent up the fast lines to relieve congestion/deal with late running/deal with problems elsewhere on the Picc, etc.). This gave me a rare (although far from being unheard of) opportunity to travel on a Piccadilly line train calling at the local stations. Apparently I wasn't the only one bowled over by the novelty - I heard tell that one Piccadilly line T/Op didn't stop at Chiswick Park because "we don't normally stop there and it was too late once I'd realised."

Even more excitingly, because there was no District line, Piccadilly line trains were being sent up to Ealing Broadway. A 1973 stock train at Ealing Broadway was just too much for me to miss; it may have been a unique opportunity.

Trains leaving Ealing Common pass over Hanger Lane junction. At this point, I should draw one of my diagrams of Hanger Lane junction, showing you what happens, but I've had quite enough of fiddling around with blue and green lines and the tube map actually does a perfectly adequate job. On the approach to Hanger Lane junction is a signal some of you may remember from a previous post which for some reason has two numbers:

The signal controlling Hanger Lane junction. Image courtesy "District Dave" (http://www.districtdave.co.uk/html/signalling.html)

For whatever reason, it's WM20 when the route indicator is on (as in the above picture) and the District line route to Ealing Broadway is set, and WM21 when the route indicator is off and the Piccadilly line route to North Ealing is set. So anyway, that's basically Hanger Lane junction: Coming from Ealing Common, you turn left as a District line train to go up to Ealing Broadway, and head straight on as a Piccadilly line train to go up to North Ealing. Obviously in the other direction it's a simple case of District line trains from Ealing Broadway heading along a right hand curve and merging with the Piccadilly line tracks coming straight down, a bit like on the tube map.

Oh, what the hey, here's a diagram of Hanger Lane Junction:

Hanger Lane junction

This is the source of the wonderful forum signature of the sadly departed "District Dave" (founder of the website I borrowed that picture above from):

"Oh - you mean I was supposed to turn left at Hanger Lane then Controller?"

Anyway, the reason behind the rambling is to explain that there's nothing in terms of the infrastructure to stop you running Piccadilly line trains to Ealing Broadway, it's just a matter of setting the points. And so that's what they did. The trouble was that Piccadilly line T/Ops aren't trained over that route, so I believe there were District line IOps (Instructor Operator) in the cab. I'm not sure who was driving and who was directing, but I imagine (since I can't see any reason why District line IOps would be trained on the 1973 stock and getting them moving is more difficult than obeying speed limits) it was the Piccadilly line T/Ops driving, with the District line IOps flagging up speed limits, signals and the like. Anyway, it's not far, which is what made it feasible.

And so:

I got up bright and early and headed down to ROV, where the WOO train was just sitting. At this stage I'd resigned myself to the 20 minute wait and was ambling over to the platform, waiting for it to pull out without me. But it didn't. I heard a train going over Woodford junction (which I assumed was from BUH (Buckhurst Hill)) as I reached the platform feeling triumphant and smug. Then the doors started beeping at me. Apparently it was a train from WOO heading to BUH and I had to hop on just in time. Happily, I got to WOO without any problems and was soon on my way to EAB (Ealing Broadway). Well, actually, I was on a NOR (Northolt) train and had to change at NOA (North Acton), which I don't mind at all - beautiful station, very quaint. It was a nice journey, seeing the stations beyond Holborn again and I pulled into a beautifully sunlit EAB feeling quite excited. And I didn't have long to wait before I saw the 1973 stock making its way into EAB. I had a nice chat with another nerd, who gave me a good tip for seeing battery locos. Battery loco(motive)s are just the name given to electric trains powered by batteries, but London Underground make good use of theirs for hauling engineering trains when the current is off for engineering work. They look like this:

London Underground battery loco. (Image courtesy "Sunil060902" (via Wikipedia))

I saw one just outside westbound platform 1 at Barons Court, which was where the possession began. (What this means is that the railway is in the possession of the engineers. This continues until they've finished, everything has been assured as safe and everyone is clear of the railway. Then, the possession is handed back to London Underground.) I also saw one on the eastbound at Chiswick Park when I was heading west and another approaching Acton Town on the eastbound.

Anyway, I hopped on the 1973 stock train and took it as far as Barons Court, in order to sample the local line running, before heading back to Boston Manor (again on the local lines) where there are superb views of the Northfields depot. The reason, though, was that I wanted a chance to use the local lines between Acton Town and Boston Manor (well, actually, the local lines merge with the fast lines just outside Northfields) on the Picc. If you look at the diagram of Acton Town, you'll see that there are four tracks going down to South Ealing, and the outer ones, visible here at South Ealing:

A view from westbound platform 3 at South Ealing looking west towards Northfields. Clearly visible on the left is the local line and its platform (westbound platform 4). The westbound fast is to the immediate right and the eastbound fast right of that. The eastbound local is out of shot on the far right. (Image courtesy "Sunil060902" (via Wikipedia))

Are the local lines and, technically, South Ealing and Northfields could be non-stopped on the fast lines. In reality, most trains these days go via the fast lines and they all stop at all stations, which is why I wanted a go on the local lines when I heard they were being used. I'm pretty sure I got a go on the way down to Boston Manor and had thought I was on the local lines on the way back, but I could be hopelessly mistaken because, thinking about it, we were held outside Acton Town on the eastbound (on what can only have been the fast line) waiting for a battery loco (and then a train from Ealing Common) to pass ahead of us. Must be getting old, can't remember which is which :P

Anyway, when I did reach Acton Town, I decided to go back to Ealing Broadway (nice to do the thing properly, both directions and all that) taking a Rayners Lane train to Ealing Common and changing for the next train through to Ealing Broadway. There I took the Central back to charming NOA and ran up to WER (West Ruislip) before doing the full trip up to EPP. It was a wonderful journey. The Sun was quite low which did affect the view on the WER branch a bit, but who cares? it was still beautiful and I was able to make EPP in the last few minutes of daylight, giving me a view of the beautiful fields up round there. At EPP I ended up meeting a friend and didn't get back to THB (Theydon Bois) until quite late. As such, by the time I made WOO there was a train in westbound platform 1 and a few in the sidings, which were joined, as I arrived, by a train from 21 road. Unfortunately, it arrived behind the others, so I couldn't really see much of it, but it was nice to witness what I wrote about back in "Woodford station". While I was there, there was someone (probably a couple of people, actually) checking all the doors, bells and whistles were working to make sure it was still fit for service. I don't know, but judging by the T/Op I saw walking away from the one that had come in off 21 road, I think this might have been the job of a fitter, who had travelled to WOO specifically for the purpose. I don't think this is done by T/Ops, but I could be wrong. The one who brought the train in off 21 road got on the next EPP train (presumably heading up to LOU (Loughton), where there's a crew depot.) Anyway, though cold, I soon made the WOO train home.

And that would ordinarily be that, but while writing about Hanger Lane junction, I was reminded of an RAIB (Rail Accidents Investigation Branch) report which I happened to come across and read the other day. This dealt with a near miss at Hanger Lane junction, which I think is interesting enough to warrant a few paragraphs :P The full report is available here: http://www.raib.gov.uk/cms_resources.cfm?file=/100322_R052010_Hanger_Lane.pdf and it makes for fascinating reading - very accessible to the layperson, too, which did surprise me. Anyway, I'll do my best to summarise it here:

On 27/03/2009, a District line train (number 103) passed signal WM1 at danger. Signal WM1 is shown on my diagram of Hanger Lane junction and it protects the junction, as well as controlling access to it, from/for trains from Ealing Broadway. "Danger", in railway terminology, refers to a red signal and this type of incident is called a SPAD (signal passed at danger).

Before reaching WM1, trains from Ealing Broadway first encounter signal WM100 (74 m before WM1). WM100 is involved in speed control signalling and it helps to prevent a crash from occurring at Hanger Lane junction. The consequences of a train passing signal WM1 at danger and failing to stop before it had travelled onto the junction could be catastrophic if a train to/from North Ealing were to collide with it. As a result, if signal WM1 is at danger (is red) signal WM100 will also be red until track-side equipment detects that the train is travelling at no more than 10 mph. Then, and only then, will signal WM100 clear to green. Also provided, on the same signal post, is a repeater signal RWM1. RWM1 is yellow if WM1 is red and green if WM1 is green. This gives the driver of a train approaching WM1 additional warning. RWM1 is off if WM100 is red. All of this is well-explained in the report, but since I've taken on the job of summarising it, I'll provide my own diagram here to help make things clear:

1. When signal WM1 is at danger, WM100 is also at danger until an approaching train is travelling at no more than 10 mph. RWM1 is off because WM100 is at danger. So, let's suppose that a train from Ealing Broadway is approaching at >10 mph and WM1 is at danger. This is how the signals would be. This is also how they would be if no train were approaching at all. WM100 only clears to green when a train has been verified as travelling at no more than 10 mph, or when WM1 clears to green.

2. When signal WM1 is at danger and there is a train approaching at no more 10 mph, signal WM100 clears to green (or "proceed"). RWM1 then comes on and is yellow because WM1 is at danger. This, then, is what happens next when our train from Ealing Broadway has slowed down to 10 mph or less.

3/1b.  When signal WM1 is green, WM100 is also green. Since WM1 is green RWM1 is green. So, if our train from Ealing Broadway had slowed down to 10 mph or less and then WM1 cleared to green before it had passed WM100, the T/Op would see green over green. This is also how the signals would be if WM1 had been cleared before a train had begun to approach, however fast it was travelling.

So how does this help? All signals on manually driven lines have trainstops, which look like this:

A raised trainstop. (Image courtesy "District Dave" (District Dave signalling))

When the signal is red, the trainstop is raised (like in the picture above). All manually driven trains are fitted with tripcocks, which will hit the raised trainstop, if they pass the signal at danger. On these trains, the emergency brakes are held off by air pressure in the brakes. When the tripcock hits the trainstop, it releases the air from the brakes and so the emergency brakes come on, stopping the train automatically. Obviously, if the signal is green, the trainstop is lowered and it carries on as normal. So how does this help? Well, the point is that, if a train passes signal WM1 at danger, it will be tripped to a halt and so should not reach the junction and cause an accident. Or at least, that's what you want to happen, but what if the train's going too fast and it can't stop in time? That's where WM100 comes in. WM100 also has a trainstop, which will not lower until the approaching train is travelling at no more than 10 mph. If it's travelling at >10 mph when it passes WM100, it will be tripped to a halt long before it's reached the junction. That way, it is ensured that the train is travelling slowly enough that, when it reaches WM1, if it should pass it at danger, it cannot reach Hanger Lane junction and cause an accident. RWM1 also helps by providing additional information about the aspect of WM1. Obviously, if WM1 is green, there is no need to enforce this 10mph speed limit, because the train can safely proceed onto the junction as normal, travelling at full line speed. This is why WM100 is green when WM1 is green, whatever the speed of the approaching train.

This is WM1; naturally, there are other signals protecting and controlling Hanger Lane junction. Signal WM2 is the station starter signal at North Ealing and controls passage over Hanger Lane junction for Piccadilly line trains from North Ealing. Our old friend signal WM21 obviously controls passage straight on over Hanger Lane junction for Piccadilly line trains from Ealing Common. (WM20, as mentioned above, controls passage onto Hanger Lane junction for District line trains heading to Ealing Broadway. However, trains taking this route will not cross the path of any other train.)

So, that's the safety equipment, back to the near-miss. In this case, everything essentially worked as designed. Train 103 left Ealing Broadway at 17:21 and headed on towards Hanger Lane junction. As the train was approaching, WM1 was at danger and so, therefore, was WM100. The T/Op dutifully slowed his train to <10 mph and WM100 cleared to green. RWM1, of course, turned yellow which, it appears, was not recognised by the T/Op. The T/Op failed to correctly sight WM1 as being at danger and did not notice, until it was too late, that the tripcock was raised. Immediately, he applied the emergency brakes, but passed WM1 at danger, at low speed. The train was tripped to a stop, only about 5 m from WM1, well short of Hanger Lane junction, at 17:23.

The T/Op presently left his cab and informed the signaller of the incident by means of the signal telephone. The signaller undertook various actions in an attempt to make the area safe for train 103 to proceed across Hanger Lane junction. This would obviously require that no train be allowed to cross Hanger Lane junction to/from North Ealing, for the paths of the two trains would intersect, almost certainly causing an accident. To achieve this, the signaller held the Piccadilly line train that was at North Ealing on the eastbound (train 340) in North Ealing (at signal WM2). This train could not, therefore, proceed onto Hanger Lane junction. Train 252, the previous eastbound Piccadilly line train from North Ealing had already cleared Hanger Lane junction and would not be a problem. The Piccadilly line train approaching Ealing Common on the westbound (train 326) was also held at signal WM23A. This prevented the train from entering Ealing Common and, therefore, prevented the train from proceeding towards Hanger Lane junction. The signaller informed the T/Op of train 103 of what he had done and instructed the T/Op on the action he should take, telling him "carry out that procedure, OK?"

Although, I believe, the signaller maintained that he had not intended to clear train 103 onto Hanger Lane junction, the T/Op believed himself cleared to proceed onto the junction and began preparing to move his train. Unfortunately, the signaller had neglected to hold the westbound Piccadilly line train (316), which had been at Ealing Common, heading towards North Ealing and on to Uxbridge, when he had undertaken action to hold the other trains. While everything else was happening, train 316 had left Ealing Common and signal WM21 had cleared train 316 over Hanger Lane junction (WM21 is a semi-automatic signal, as - in fact - are all of the signals I've been discussing, which means that it is usually controlled by the signalling computer, but can be operated manually by the signaller. In this case, the signaller had not taken control of WM21 and it cleared automatically, for train 103 had not passed far enough past WM1 to alert the computer that it was not safe to clear WM21). 316 presently passed over Hanger Lane junction as the T/Op of 103 was preparing to move his train. Had the T/Op got his train moving earlier, it would have been a bad day to be on the tube.

Happily, it was just a near-miss, nothing came of it. Indeed, it's important to remember just how safe the tube is and just how rare major accidents are. The vast majority of the few serious incidents on the tube are not accidental and the number bandied about on the Wikipedia page (taken from a 2003 article in the Economist) suggests that there is(/was) only one fatal accident for every 300 million journeys. One of the reasons for this, of course, is full and open investigations, like these, and prompt and appropriate responses to the results. Another, of course, is the safety equipment - some of which I've already talked about and a big one is the staff. Of which, it seems, we will get fewer; but that's what happens when you put a TV idiot in charge of running a major capital.