I’m going to learn why and how trains generally don’t crash into each other.

The trouble with videos about trains is that there are two potential audiences:

people who don’t care about trains,

who need to be convinced that the video’s worth watching,

and people who really care about trains who will want to skip all the basics

and would like enormous amounts of nerdy detail.

This video is for the first group, because despite appearances,

I am not that much of a train nerd!

But in my defence, if you are a train nerd,

you almost certainly already know more

than I learnt in my time

at signalling school.

So, exactly what you would not expect…

…in the middle of a meeting room in an office building in Manchester.

Network Rail are the folks

in charge of the rail infrastructure across Britain,

and that’s one of the places they train their signallers.

I say one of the places, because

as you can see, the equipment there is a little old-fashioned.

It’s for the older parts of the network.

My tutor was Nick, and he started out with some very reassuring advice.

One of the excellent things about this, the Victorians got dead right,

is it’s designed to fail safe. -Right.

You can’t get it wrong and cause a crash

unless you manually override stuff and start talking to drivers.

-Oh, okay. -So we don’t like talking to drivers.

That’s why we put lights and boards and stuff out in the world

so they can just follow our instructions.

If we’re doing it that way, you cannot cause a crash.

The system stops you.

Nick turned on the system

which kicked all sorts of relays and switches into action…

(switch clicks) Hey!

Ah, that’s lovely.

And then we were into Signalling 101.

As a heads up, this video has been checked through by Network Rail for security

because they did let me inside critical national infrastructure.

They did ask me to blur a couple of things,

but all my words and opinions are my own.

They had no editorial control.

Obviously the main event is all the levers.

Yep.

Each lever corresponds to a single function.

Yep.

You cannot pull the levers in the wrong order.

-Okay. -So to prove that to you,

if you try and pull number eight now,

so, just squeeze the catch and pull it towards you...

-Oh. -It won’t let you do it.

It won’t let me do it. Okay.

So again, this being a simulator, it’s not quite how it is on the ground.

-Yep. -On the ground,

that’s a mechanical interlock, -Right.

physically stopping you from doing it. -Yeah.

So, the reason that signal boxes tend to be quite tall

is what happens underneath is a big mechanical computer.

Yep.

It was designed really well in the 1880s, 1890s.

We haven’t touched a lot of those since,

apart from for maintenance and stuff like that, because it works.

Because it works.

I just nodded along then,

and it wasn’t until reviewing the footage afterwards

that I realised quite what a big deal that is, and it’s not obvious.

When a signaller pulls a lever like that,

and I know some parts of the world say “levver”, I’m British, I say “lee-ver”.

Anyway, when a signaller pulls a lever like that

up in an old-style signal box by the side of the track,

they are physically

moving the rails, the switches, the “points” that direct the trains.

A lot of the time these days that lever might actually trigger a motor

to do some of the hard work,

but for a lot of points, certainly older ones,

there is a direct physical connection:

each lever is pulling on gears and pulleys and cables

and directly moving either the actual rails

or the semaphore signals that tell drivers whether it’s safe to continue.

And so when Nick said, “mechanical computer”, he’s right.

Dangerous positions are either impossible,

or they’re possible only if a driver ignores a signal.

You physically cannot pull the lever to say it’s safe to continue

if the points aren’t set properly.

It’s interlocked mechanically.

Which is also the reason there’s a specific way you pull the levers.

Nick got me started on a simple one.

-So, if you just pull number nine… -Pull number nine.

Yeah, pull number nine.

(lever clicking)

-Okay. -Okay.

Best to have two hands on, one to hold the catch

and one to actually do the pulling of the lever.

-Okay. -It’s really easy to slide up the catch

and it’ll go flying back in. -Oh, okay, yeah.

Yes, ’cos these are not actually hooked into a giant thing

that wants to pull it back.

Because they’re physical and fail-safe,

if your hand slips off,

all that mechanical weight is going to slam that lever back,

and that could break something.

So, there’s a specific technique: unlock the “catch-handle” with one hand,

then wrap your other hand around and pull the lever.

With that technique learnt, a big red light on my board illuminated

in block 302, just before Signal 3,

which meant a train was approaching.

Or at least, a simulated train was possibly approaching.

I thought it was stopped at Signal 3, but we don’t know that.

No. So it’s somewhere. We don’t know its state.

-Right. -We just know it’s there.

’Cos there’s a circuit in that bit of track

and it’s completing the circuit between the rails.

So we know there’s something in Block 302. -Yes.

-It may be moving at speed. -It may be moving. It may not be a train.

-Oh. Right. -Everything’s designed to fail-safe.

So, that could be something conductive across the rails…

-Right. -…that’s detecting.

-Yep. -That could be a break in the rail

if the circuit’s not made, -Right.

then that will show up.

So, the engineers will tell you a track circuit detects…

It proves that there is not a train present.

Right, okay.

If the lights are off,

that section of track is safe.

That’s why there’s two bulbs in each light, it’s a redundant system,

along with a lot of other fail-safes I’m not covering here.

It might seem like the light means “train”,

but no, unless you can see the train, you can’t be certain.

That light actually means, “There is danger.

“Do not send another train into this section.”

And if we clear the signal in front of it, and if it was real,

we’d look out the window over there somewhere,

and we’d see a train, hopefully, right? -Yeah, yeah.

And then we’d be able to tell, is that moving, is that stopped?

If we clear a signal and it’s a train, hopefully it’ll go.

-Yeah. -Okay, so if you pull number three…

So number three is the one right in front of it.

-Again, ideally it’s a second hand on top. -Oh, yeah, two hands, two hands.

-Yeah. -Yeah.

Whoa. (lever clicking)

-And that’s why. -Let it go. That’s why.

You’ll see your repeater down here will go from red to green.

-It’s green, yeah. -And, well, the train starts moving.

So it’s now covering 302 and 303, and now 302 has gone.

-Yeah. -Oh, in fact, I can see it moving along.

304 has lit up.

There are no signals… 305’s lit up.

It will presumably stop, hopefully, at number four just here.

-Exactly. -Having moved along the board.

-Yes. -And having moved along our track.

-Yeah. -Okay.

So, hopefully it’s over there somewhere now.

Yep. And it would now make sense,

we’ve only got 306 lit up,

so we know all the other sections are now safe.

No, we don’t. You can’t let a train into 303, 304 or 305.

No.

-Because there’s no signals between them. -Exactly.

Just because a small section

is clear doesn’t mean I could send a train into it.

There were no signals between each of those lit sections,

no way to stop any second train following along,

so, I couldn’t put a train into that block.

That is called “absolute block” signalling:

no more than one train per signalled block at any time.

Easy enough if my board was the whole railway...

but it’s not.

These are the most important piece of equipment actually,

as much as this is the pretty bit and that’s the impressive stuff.

-Yeah. -These are the most important things.

These are how we talk to the other signallers,

the other signal boxes. -Okay.

So, as far as we’re concerned, there are three other signal boxes involved.

Two in that direction and one in that direction.

Two in that direction. One in that direction.

-These are block indicators. -Block indicators, we’ve got two that way,

one that way. -Exactly.

We cannot send a train to another signal box without their permission,

and it’s them that tell us whether it’s clear.

So, I would need to say “line clear”... -No.

-Or “train on line”? -You would ask for…

You would send a bell code which equates to, “Is the line clear”?

We’ll explain bell codes in a minute.

The important thing is that I have to ask the other signal box,

“Is the line clear?”.

The signaller at the other end will look out the window...

-Yep. -...check their book...

Yep.

...check their diagram, and go, “There’s no trains

“and the last train passed clear. Yes, the line is clear.

“One can approach me.” -Right.

In the same way,

they can also ask you, is your line clear? -Yep.

And you go, “Yep, I’ll check my book. Yep, the last train’s passed clear.”

There’s nothing outside. Look out the window.

There’s no trains there. -Yes.

-And that point, you can go to line clear. -Okay.

That will show at the top on theirs

and it will release their signal that enters the block section.

-Right. -Okay?

So, my signal box

can lock out levers in the next signal box.

That signaller will get in touch, ask if the line’s clear,

and until I confirm that it’s clear with my “commutator”, that switch,

they cannot move their levers. It works the other way too.

But how do we communicate over that distance?

Well, remember that train

that was lighting up on my board?

The next job was to ask the next signal box if I can send it on to them.

Well, first of all, I need to put signal four back.

Yeah, let’s have number four back.

(lever clicking)

The next lever to pull would be number 5, for signal 5 at the end of my section.

It’s a red and yellow lever

because it handles a red stop signal

and a yellow “slow down, the next one’s red” signal, those two operate together.

There’s also a white band in the middle. That’s not just for aesthetics.

-Okay. -You’ll notice there’s one on one-one,

one on one-five as well. -Yeah.

That tells us that these levers are locked by the next signal box.

-Oh, right, okay. -So, it’s our last signal.

-So, I literally can’t unlock that? -No, try and pull it.

Two hands.

(lever clunking)

Literally cannot unlock it until…

-Weatherall lets us. -Yeah.

-So, I need to go and ask for permission? -Exactly.

Nick took a seat, and acted as the distant signal box.

We’re now at the point where we’re basically at the limit

of what Victorian engineering could control from where you are mechanically.

Right, ’cos it’s only so far you can pull a wire to.

-Exactly. -Yeah.

So, there is now some distance that has no infrastructure on it.

-Right. -Okay, so there’s no signals,

there’s no track circuits.

-One train at a time. -Exactly.

So, we now need to ask the next signal box,

is there anything stopping you from letting a train approach you?

Yeah.

So, the first thing we need to do is summon their attention.

-Okay. -So, on…

-It’s gonna be a bell. -It’s gonna be a bell.

I’ve got a grin on my face, it’s gonna be a bell. Right...

Just press the tapper once, (beeping)

and you’ll hear a beep at this end. -Yep.

What’s quite weird in real life, you hear nothing.

-You hear nothing. -You hear a click.

-Okay. -There is a bell going off

at the other end. -Right.

-Okay? -Okay.

-So, when Weatherall are up... -Yep.

...they put their newspaper down, whatever else, they’re ready to speak to you.

(bell ringing) Oh, okay.

-They say, one back. -One out, one back.

Exactly. All of these exchanges are repeated.

-Yep. -And you’ll find if we see any voice comms

and stuff like that, it’s exactly the same.

-Right. -Everything is out and back.

-Okay. -It’s not understood until it’s repeated.

-Okay. -So, the next thing we need to do is ask,

is the line clear for a stopping passenger train?

-Okay. -So, you’re going to ring three...

-Yeah. -...short pause, and then a one.

Three, one.

(beep beep beep, beep)

So there’s about…

I want to say 12 variations of, “Is line clear?”

-Okay. -If we went to Stockport,

you’d add another 10 or 12. -Wow. Alright.

I’m getting the really simple version of this. Okay.

Three and one. Is the line clear? Three and one.

-Exactly. -Okay.

So, we’ve asked Weatherall, is the line clear? Three and one.

-Yep. -Okay?

What they’re doing now is looking out the window, checking the book,

making sure the line is clear. -Yes.

Okay? When they’re happy...

they move to line clear. -Oh, so I can see that up here.

Yes. That little arrow has gone, boop, line clear.

Exactly. So, you can see line clear.

-Yep. -They also respond.

(ring ring ring, ring)

-Echoed out, echoed back. -Exactly.

-Okay. -And your signal is now unlocked.

So, I can now unlock number five, let the train go to Weatherall...

Two hands.

(lever clicking)

-Okay. -You can see the signal’s gone green.

Yep. Just here.

And we can expect that the train is going to start moving now.

And then as soon as 309 up there says it’s clear...

I’ll put the signal back.

We also need to tell the next signal box, the Weatherall signal box,

that the train is actually coming.

So, we now send two.

(beep beep)

Train coming.

(ring ring)

“I understand the train is coming.”

Yep. Train entering section.

They reply, and change to train on line.

This thing has gone to red. There is a train on the line.

They know there’s a train on the line. -Exactly.

It’s not even worth me asking, ’cos I can see that there’s a train on the line.

-Exactly that. -Got it. Okay.

And it’s physically now locked our signal to stop us from sending another one in.

-Okay. -Okay?

Yes.

This is an old-fashioned system, more than a century old,

but it is still in use on some of the slower, smaller train lines.

So...why not update it?

Why are there still lines that run this way

when there’s surely a better, modern solution?

You wouldn’t get any more trains through.

They’d still get to a bottleneck at the other end.

So, it’s not worth spending hundreds of millions of pounds to replace it all.

-And it would be hundreds of millions. -Oh yeah, absolutely.

And all the disruption that comes with it.

You’ve got to close the line while you do it, all that sort of stuff.

Yeah.

So, we might as well just carry on using this safe system that works.

-Yeah. -And people enjoy doing it.

Yeah! (laughter)

And in a lot of cases there’s a benefit to having people out by the lineside...

-That’s true. -...watching the trains go past.

They can see if there’s issues with the trains and all that sort of stuff.

-Yeah. -You may or may not have noticed…

I haven’t. -…that all trains have red lights

on the back. -Oh, yeah.

-Yeah? -Headlights on the front,

red lights on the back. -Yeah, lights on the front,

reds on the back. -Yep.

Those red lights serve a purpose to us.

That is proof that that’s all of the train.

-Oh! -Yeah?

So in the old days, when trains were all loose-coupled

and didn’t have continuous brakes… -You haven’t lost a train on the way.

-Yeah, yeah. -A carriage on the way. Huh.

When trains didn’t have continuous brakes and they weren’t very well...

they were loose-coupled... -Yeah.

...that would happen. Bits would fall off.

So, if you stick a lamp on the back one,

and the one with the lamp doesn’t turn up, there’s still some midsection.

There’s still a carriage there.

On modern trains, that wouldn’t happen.

The brakes would come on automatically and the driver would have to go investigate,

but still, that’s why trains have red lights at the back.

They’re approaching signal 4 which is green?

Exactly. So, conventionally we won’t touch a lever

unless we’re going to do something with it.

It’s surprisingly easy to catch the handle. The lever flies back in...

-And it’ll fly back. -And just as the driver’s approaching it,

the signal goes back to danger. -Oh!

-And they get very upset with that. -They do.

-You have to be incredibly magnanimous... -(laughter)

...when you explain that you didn’t mean to

and you’re terribly sorry and you won’t do it again.

A “signal passed at danger”, a SPAD,

is a really serious thing on the rail network.

They are very rare, and most of the time they’re minor.

But they’re always investigated,

and if it’s a train driver’s fault,

it can be career-ending, or certainly career-limiting.

They’re getting a green light that says, “Go, go, go, all good.

“You can go at 100, 125 miles an hour”. -Yeah.

-And a train takes miles to stop. -Yeah.

-If you now go, “Stop!”... -Yeah, no.

-...they go, emergency button. Urgh... -(laughter)

-Wait. -They’re bricking it.

And everyone behind on the train has suddenly had their coffee cups fall over.

-Exactly. -Yeah.

They come to a stand and you just go, “Sorry.”

-“Soz! Soz.” -Exactly.

There were a few more basics to learn.

Different bell codes for different sorts of trains,

some signals that change to danger automatically,

“facing point locks”,

and the physical lockouts called reminder appliances

that get put over levers to remind signallers that something’s out of use

or needs special attention before it’s moved.

But it turns out you can learn the basics of signalling in half a day.

After a couple of hours of training,

I could run a train through the simulation both ways

without much prompting.

Dealing with a simple railway that’s running well

is actually not all that difficult.

The rest of the months of training

is about how to deal with things when they don’t work as expected

on a system where the consequences of getting it wrong can be deadly.

Basically your next nine and a half weeks

covers virtually every light, every button.

What if any one of those doesn’t do what it’s designed to do?

-Yeah. -What if this light flashes?

What if this buzzer goes off?

I did also get a look at the modern equivalent.

The high-speed lines on the British rail network

all run using much more recent systems.

This is intimidating. -(laughs)

Yeah, so this is very different to what you’ve seen this morning.

-Yes. -But very, very similar.

Okay. So I can see the route diagram here is laid out the same as the big board.

-Yes. -Okay.

The key differences are, there’s more of it.

-Yes. -Um...

That’s really it.

The modern system uses a lot of screens

and lets you set longer routes instead of individual signals,

but it’s basically the same process,

just covering a much, much wider area and without as much physical effort.

And of course, it’s modern electronic signals and lights, not semaphore arms.

That computer’s running the same software

as the ones in the real signalling room next door

that we were very much not allowed to go in.

It’s just that the workstation I was using

wasn’t hooked up to the real rail network,

just to another computer running the sim.

All the areas that the signallers cover are graded in terms of difficulty.

The simulation I tried with the levers is somewhere about a grade 1 or 2.

-This one, Wavertree, is a grade 6. -Okay.

-We go up to a grade 8 in the ops floor. -Right.

And that’s places like Manchester Victoria, Liverpool Lime Street,

kind of your busy termini. -Yep.

We do have grade 9 signals over at Manchester Piccadilly,

which is the Piccadilly station, 14 platforms.

There’s a movement about every 30 seconds.

(exhales) Okay.

And they work in two hour shifts at a time, because there’s just…

they don’t stop for those two hours.

And if you’re wondering why they haven’t upgraded from trackballs to touchscreens:

it’s because, just like the old Victorian engineering,

it was built to last and built to be reliable.

And with experienced signallers having decades of training on it,

there’s really no advantage to changing it.

So with that, we headed out to see signalling for real,

just over the Cheshire and Derbyshire borders

at a little station with a signal box in a village called Dinting

which has a strange triangular arrangement of tracks.

We got off our train on one side of the triangle.

After that, it headed on to Glossop,

which despite looking like the end of the line, isn’t.

After Glossop, it would go back, around the next bit of the triangle

passing by Dinting, and stop at Hadfield.

And then it would do the same route in reverse:

round the triangle at Dinting,

back to Glossop, stop there,

back to Dinting, stop there,

back to Manchester.

All of which was under the control of signaller Craig.

So, this actually sort of feels familiar now, having seen…

So, yeah, so the equipment is very, very similar.

-Yeah. -There’s some detail changes.

The catch-handles are slightly different, but it’s exactly the same concept.

The content on the diagram will be the same.

The bell code that Craig will be doing

will be exactly the same. -Right.

By the time we’d set up the cameras,

the train had already made it all the way to the end of the line at Hadfield,

and everything was set up for their run back to Glossop.

-So, lights are on up at Hadfield Station. -Yes. So, the train is up there...

-That would be up there. -...the one that we got off.

-Second point of the triangle. -Yes.

So, you’ll recognise again the block instrument.

You can see from what we discussed, what we did earlier, there’s one coming…

-Yes. “Train on line.” -They’ve told us it’s coming.

Schrödinger's train, it’s somewhere on the approach to this signal.

(loud electronic beep) Oh!

(laughter)

I’m immediately backing off. I was like, have I done something there?

It’s just a beep to tell us that the train’s left Hadfield.

-Okay, right. -And it’s on its way.

Turns out there are all sorts of beeps when trains pass various signals,

because once again, I’d only covered the very basics.

Craig showed me the rulebooks.

When things go wrong…

Oh!

Okay.

-Right, yep. -That’s what we’ve gotta…

Signallers need most of those rulebooks in their head,

and learning it takes a long time.

How long did it take to get qualified?

About a year.

I had to do ten years of signalling school

where you learn your regs, your regulations and your rules.

-I think you just said ten years. -Sorry, ten weeks!

It felt like ten years! -(laughter)

Yeah, that was probably the hardest thing I’ve ever done.

-Yeah? -Including my degree.

A signaller has to be trained not just as a generic signaller,

but on each specific line or box that they’ll be dealing with.

So even though you might get a box which is just a straight up and down line,

there’ll be something in there that can trip you up.

Love the job though, it’s good.

It’s the only job I’ve ever had where when I started going around boxes

and speaking to signallers and stuff saying, “Do you like it?”

every single one’s like, “Best job in the world, it’s great.”

And I do, I love it.

I wish I got into it 20 years ago.

By this point, the train we’d been on had made it back to Glossop.

We’d been able to see it

just out of one of the signal box windows as it passed through the triangle,

and so it was time to set up its route back to us.

(lever clunking)

So, his route’s been set now.

Yep, so we’ve now got confirmation that the points are in the right place.

-Yeah. -And we’ve got a green signal

on number 19, which is just there. -Just there.

So, Glossop train...

is going to start heading back soon. -Yes.

And then on your CCF, you can also see that the route’s set as well.

-Oh, yeah! -The line that’s thicker,

and it showed that I’ve cleared the signal.

Craig referred to the CCF there,

which is the wonderfully named “Control Centre of the Future”!

Good news: we’re in the future, and that control centre,

that display, is working.

It’s just another copy of everything that’s going on,

but it’s rigged into the Victorian engineering.

9 into 8 heading towards us,

and because all these signals are now…open? What’s...?

I don’t know what the right term is. -So, we’ve cleared that signal, one-nine.

-Cleared. -So that’s cleared a route

all the way through here... -Yeah.

...and up to three-two.

Next job,

offer that train to the next signal box down the line using the bell codes.

So, I’ll call attention. (lever clunks)

(bell rings) I’ll give him the train class.

(tap tap tap, tap)

(ring ring ring, ring) Class 2, so it’s 3-1.

I’ll wait for him to go “line clear”.

-Line clear. -So, now I can clear my 32 signal.

(lever clunking)

That’s 32. Get the correct indication.

And then I’ll tell him the train’s entering the section.

(tap tap)

-And he’ll go, “train on line”. -Train on line.

(ring ring)

And that’s the train we were on there.

That’s the train you were on.

(train clacking)

No, I don’t know why my camera decided that it should point downwards there,

but, yeah, that’s the train we’d been on.

At that point, another track section lit up on the board.

-So you’ll see… -Oh, yeah, someone’s coming in.

So this one’s coming in now, so...

I’m now, because it’s cleared the section where I’ve got my points,

-Yep. -I can now set his route in.

-I have to ask... -Go on.

It’s a cheeky question, feel free to say no.

Can I…can I pull a lever? If that… -Yeah, yeah.

(laughter)

-Thank you! -Yeah, of course you can.

Alright, so what am I going to do?

32, it’s going to go back. It’s going to cancel off the last route.

-Okay, so... -Pull the handle

and push the lever forward. -Slightly different lever, okay.

(lever clunking)

-Okay. -So that’s put this signal back to danger.

Right.

Now what you’re going to do is cancel the points

and put them back into the neutral position.

The lever for points was a little different:

I had to push it back most of the way,

then wait for confirmation from the light,

you see that “N” turning on?

Only then would it let me rock it back a little and lock it into place.

That’s because on that box, I’m not physically moving the points.

I’m sending signals to a motor.

In theory, that could be a button these days,

but why change what works and what people have trained on?

-So this one out? -Yeah.

(lever clunking)

-This one in? -Yep.

-Yeah? -Yep.

Resistance, wait for the light.

Light, all the way back. (lever clunking)

-And then this one? -You can leave that out.

Can leave that.

-So... -(laughter)

A reminder that not only is there a professional signaller watching me,

there is the guy who teaches the signallers how to do their job,

and also someone else from Network Rail that you can’t see.

So, you’re going to be pulling 16,

17, and then 26. -Okay.

-16, 17, 26. -Yeah.

I cannot believe you’re letting me do this. Thank you, folks.

-It’s alright. -Sixteen.

(lever clanking)

Wait for it. Wait for the light.

(clunking)

-Push. There you go. -There we go.

Seventeen. -Yep.

(lever clunking)

(clunking)

So, that’s those points.

That’s the points are now in the right position.

-And locked. -And that wait that I had

was waiting for the electronic confirmation that the points are in the right place.

And they’re locked, yes.

So, points are in the right place. We can now give him a green light.

Yep. (lever clunking)

-Indication. -Indication’s on.

With lots of time to spare. -Yep.

And now?

Passengers are loading at Glossop and whenever he’s setting off.

Then you’ll get that beep again when he sets off.

Right!

-You just need to do that. -(laughter)

Thank you so much, Craig.

You just need to do that about 500 times a day.

Right!

-We’ve got a train to get on. -Yeah.

Thank you so much, Craig!

If you want to see next week’s episode right now,

you can on Nebula!

Every episode of the England series is there one week early,

along with Originals you can only watch on Nebula.

Like 17 Pages, from Bobby Broccoli,

a documentary about one of the greatest scientific controversies of the 20th century,

told in such a way that Nebula

had to code a brand new feature for their platform.

It is literally impossible to watch that any other way!

Go in without spoilers and enjoy the ride.

And, as this video goes out,

annual Nebula subscriptions are 50% off,

just $30 for the year, which works out to $2.50/month.

There’s local pricing in euros and pounds too,

and you’ll be supporting this channel and the England series.

And if you want to know what that next episode is: well.

Next time, or right now on Nebula:

I have a flashback to my childhood,

and move a World Heritage Site by pressing a key.