Trains Bang Goes the Theory

Every morning, hundreds of thousands of passengers

all over the country rely on trains to get to work.

And that number is growing rapidly every year.

As we all know, our trains are great when they work,

but they are a nightmare when they go wrong.

Tonight on Bang,

we scrutinize our rail system and ask

how is it ever going to deal with the surge in passenger numbers?

We see how we can squeeze more trains on to the existing tracks...

All of this technology is going to revolutionize the way

our railways will be run in the future.

..how the weakest link is often the rails themselves...

When a tiny crack from a bolt hole deepens,

the consequences are not good.

And the truth behind frustrating delays caused by the "wrong kind of leaf"....

Wow. That is pretty incredible.

30 years ago, Britain's rail system was seen as a bit of a disaster.

But they've truly turned the corner.

1.5 billion people a year use 7.2 million train services

over 32,000 kilometres of track.

And passenger numbers are predicted to double in the next 30 years.

But even with new lines like Crossrail

and possibly HS2 due to come on stream, the real problem is how to

increase the capacity on the tracks we already have.

And one way to do that could be to change the way the signals work.

Signals are not only used to keep the trains apart -

they maximise capacity by keeping them as close together as is safe.

For over 100 years,

the safest and most reliable way of controlling and managing the railways

has been the Fixed Block system.

It's actually pretty straightforward.

First divide your track up into blocks potentially a few

kilometres long, separated by a signal.

This is the safety zone.

Then use the signals to let a train know

if it can safely enter a block or not.

And the simple rule is this.

If you have got a train in this block,

the next train is forbidden from entering it until the train

exits the block.

So this signal will stop this train from coming into

the block until this signal here has registered that this train has left.

As long as this rule is followed,

a collision is simply not possible.

The Fixed Block signalling system is safe and successful.

But it's also somewhat inefficient

because to remain safe, all these blocks

need to be pretty big so the tracks end up mainly empty.

With our ever-increasing demand for trains,

can the system that governs how our railways operate be improved, safely?

Well, perhaps we can learn something

from how vehicles flow on our roads.

I'm driving at 50 miles an hour

and if I need to make an emergency stop,

the Highway Code dictates that I would need a total distance of 53 metres -

that's 38m of braking distance

and 15m of thinking distance.

And if traffic builds up and I slow down,

my stopping distance, obviously, falls.

The faster I am going,

the larger the space in front needs to be.

And if I slow down, that space gets smaller.

We could increase capacity on the railways

by getting trains to follow these principles too.

It's essentially like turning a fixed block system

into a moving block.

And that's going to make all the difference.

So how would you make it work?

Well, you'd need to know everything about the train in front -

how fast it was moving, and its position.

And if you knew your speed and your position,

you could then calculate how close you can travel behind the first train safely.

Simple. In theory.

And it's exactly what they do here,

at the Docklands Light Railway in East London.

Each train's exact position is worked out

using wires laid out along the track.

These wires transmit signals to and from the trains.

The loops of cable cross over every 25 metres along the track,

and here's one of those points.

Now, the train counts the amount of times that it travels over

one of these cross points and that's the crucial part of the system.

The train can count these cross points

because the electrical signal changes direction at each twist.

This is the train's on-board computer system,

the nerve centre of the train,

and let me show you what happens when the train passes over

one of these crossover points.

The current is running in one direction as the train

approaches the crossover.

At the crossover, it flips 180 degrees, what's called a phase change.

This oscilloscope measures the direction of the signal below

and you can see how it flips as the loop passes underneath the train.

And it's this that the train registers

and counts every time it passes over a crossover.

Each pulse identifies the train's position within the 25-metre loop.

Then a second system measures

how many times each train wheel rotates.

Between these two systems, the train position can be tracked

down to just a few centimetres.

The exact speed and position of each train is relayed back to this

control centre and the computer system here calculates how

close to each other the trains can travel safely.

That information is then relayed back to the trains

so they can move accordingly.

Using moving block, the DLR's system is able to run more trains,

closer together, than a conventional fixed block system.

Which means the line capacity can be far greater.

And it's flexible enough to be able to deal with almost any

unexpected occurrence with ease.

The police just delayed the train at platform two.

Any idea why that was?

And the system is so safe, it's not only done away with all signals,

but there's also the need for on-board drivers.

Thanks to all this technology, moving block is going to

revolutionize the way our railways will be run in the future,

dramatically increasing rail capacity and efficiency.

With the technology now tried and tested,

the moving block system is being considered for roll out over

the entire national rail network.

And with this change,

we could begin to see more trains and hopefully less overcrowding.

But more and faster trains on the tracks has a serious downside.

The rails themselves wear out a lot quicker.

And this can add up to more inefficiencies, as the tracks

are manually checked and mended.

This may not look special, but that train behind me is the fastest engineering train in the UK

and it's packed with technology.

On board is the revolutionary rail measurement system called

Plain Line Pattern Recognition,

most of which is carried just centimetres from the track.

Underneath the train you've got an array of monitoring equipment.

Underneath here you've got two lasers which are capturing

the track geometry and then here you've got seven cameras monitoring

the track from sleeper end to sleeper end in incredible detail.

This level of scrutiny is required

because of the unbelievable stresses the rails themselves are under.

When the train is moving, the wheels touch a tiny surface area

of the track and in fact, if you were to take the entire length of the train,

the total area covered is less than two mobile phones put together.

So you can imagine, with 100 tonnes

of train pressing down on that tiny surface area, it's got to take its toll.

Most significant is a phenomenon called rolling contact fatigue,

which is a result of stressing the rail as the wheel

presses down over and over again.

In fact, over its lifetime, a single rail will end up

stressed by over a billion tonnes' worth of trains.

And the impact is worse at bends, where

the full weight of the train is thrown at the outer rail.

This is an example of rail fatigue.

If you look, those tiny cracks may look really innocent.

But over time, they are going to deepen and spread.

And eventually, they can become very dangerous.

The consequences are similar to what happens

if I start bending a hacksaw blade, in that initially with that pressure

you are OK, but with continued pressure, that's what happens.

The cracks deepen, the rail splits apart and you are in deep trouble.

Good evening. Four people have been killed and dozens injured

after an Intercity train derailed at high speed in Hertfordshire.

On the 17th of October 2000, an Intercity 225 bound for Leeds

entered a bend just south of Hatfield at around 185kph.

As the forces mounted, the outer rail failed and the whole train

derailed. Four people lost their lives and over 70 were injured.

And rails can fail in other ways too.

This piece of rail had a manufacturing defect

and with pressure, it grew

and you can see that is not looking healthy at all.

And then here, this is what happens when a tiny crack from a bolt hole deepens

and as you can see, the consequences are not good.

Rails can be vulnerable in a number of other different ways.

Their fasteners can come adrift, the joints can be misaligned,

and the clamps go missing.

Any one of those can cause a disaster.

Rail maintenance is a huge commitment for Network Rail,

costing millions of pounds a year

and it's one they obviously take very seriously.

Up until now, most of the inspection work on the railway

has been done by men walking along the track,

spending millions of hours

checking and rechecking the state of the rails.

But that is far from ideal.

-The problem with manual inspection is that it is very slow

--

each rail has to be scrupulously surveyed by experts every few weeks.

Inspectors on the tracks is always a safety issue and of course, all this

time required for inspection ends up having an impact on passengers too.

But the new measurement train should make a real difference.

We're travelling at 100mph and if you take look at that

screen there, you can see the live images coming from the cameras

underneath the train.

All of the data is being collated and stored here and then

when we get back to base, the drive can be removed and analysed.

The software then interprets the images and identifies potential problems.

Those problems can be then checked by inspection experts, who can

order the appropriate action.

It could be the start of a crack appearing in a joint or a weld

and if it goes unnoticed,

that weak point will carry on getting damaged.

We try to find it early before a problem occurs.

Do you know, the quality is just astounding,

bearing in mind that the train can be travelling at over 100mph.

Finding cracks and things like that is very easy

because you can zoom in so for and the quality is perfect.

When a fault is found, their position is marked by GPS and

repair teams are sent direct to the problem within days or even hours.

At the moment, the new measurement train is covering

over 100,000 miles a year,

and potentially, it can be

rolled out across the whole of our railway network,

significantly reducing trackside inspections

and ultimately increasing rail capacity.

Matt Brassington is the project manager.

Can this technology really replace the experienced

eye of the track inspector?

The inspectors on the train

are actually qualified track inspectors themselves

and the software that we have

replicates what they would do on the ballast.

The system in its totality is far, far better than you would

get from a track patroller.

How many hours will this save you?

Originally it took up to about 1.5 million man hours

to inspect national Network Rail's infrastructure.

This has now been halved by the introduction of plain line pattern recognition.

And this has a direct impact on passengers.

Fewer hours wasted by maintenance patrols on the tracks

means routes are not out of action and can carry more passenger trains.

So that's more convenient for passengers

and much safer for the inspection crews.

The New Measurement Train is an impressive piece of technology

which should put an end to some of those frustrating

delays on the line and also prevent faults from becoming tragedies.

But there is one problem that not even this train can sort out

and that's the age-old issue of leaves on the line.

It sounds like the worst excuse imaginable.

How could something as insignificant as leaves

affect a 100-tonne train?

But they do.

In 2002, leaves caused over 500 days' worth of delays.

And it's ultimately

because of how the train's wheels roll on the rails themselves.

One of the reasons that trains are so efficient at pulling heavy loads

whilst expending very little energy is the fact that their steel wheels,

running on a steel rail,

produce very little of what's called 'rolling resistance'.

When any wheel rolls across a surface,

the mass pressing down in it will cause it to deform.

The larger that deformation, like in the case of a semi-flat tyre,

the greater the rolling resistance.

As the wheel deforms, energy is lost

and I can tell you, it makes it much harder to cycle a bike.

On a train, the deformation in the hard steel wheels

and on the rail is incredibly minor,

which equates to a tiny amount of rolling resistance.

But when it comes to stopping and starting,

steel on steel presents some real problems.

Let me show you what I mean using these two steel weights

and this steel plate.

The only difference between these two bits of steel

is that there is a bit of rubber on the underside of this one.

Watch what happens when I tip the plate.

Of course the one without the rubber beneath it

slips to the bottom quickly.

Luckily, under normal conditions, there is just enough

grip between the wheels and the track to allow the trains to

start with ease and, more importantly,

to stop safely.

But when there are leaves on the line it's a different matter.

You see, leaves are made up of about 80% water,

and the rest is a complex combination

of other substances, including cellulose, pectin

and a type of fatty acid which

happen to have lubricating properties.

Research has shown that soggy, slippy leaves are actually

sucked onto the track by the passing trains.

And once on the track, they are crushed to a pulp by the wheels.

The result is a thin black layer of crushed leaf matter,

about 25 microns thick -

that's thinner than the width of a human hair.

And when you get a little bit of rain,

this layer becomes incredibly slippery.

This means that at peak time in the autumn, to avoid slipping,

trains have to accelerate and decelerate

much more slowly than normal, resulting in frustrating delays.

So what does leaves on the line mean in terms of stopping distances?

When Nick and Ian slammed on the brakes at the stop flag over there,

this is where they came to a stop,

and it's roughly where they would end up under normal conditions.

But what would happen if there were crushed leaves on the rails?

We'll simulate the slippery effect of leaves by using

a mix of washing up liquid and water.

This stuff is actually less slippery than crushed wet leaves,

but it's easier to apply, which is why rail companies use this

when they are training drivers to handle low-adhesion conditions.

Right, let's see what happens now when the train tries to stop.

All right, lads.

Here were go - they are about to slam on the brakes at the stop flag.

Whoa...

Wow.

That it pretty incredible -

three times the distance it stopped originally.

Our test is limited to a train speed of 16 kilometres per hour,

and we only prepared 18 metres of line.

Imagine what the effect would be on a 200-tonne express

travelling at 160 kmph.

And this is ultimately why leaves on the track

is no joke.

And you might think to yourself, "Why not just

"cut the trees bordering the railway line?"

But it's not as simple as that.

The answer goes back over 50 years...

Back in the steam locomotive era,

line-side vegetation was kept down by fires caused by sparks

from the trains engines.

But as new diesel and electric trains took over from steam,

the trees thrived.

Now the trees are mature.

Of course, conservation plays a part here,

but even if ecologists agreed,

it would cost £2.5 billion to remove the trees along our tracks,

making it financially unrealistic.

Instead, Network Rail can use high-speed water jets

which blast the leaves off the track,

and lay a mix of sand and aluminium, to aid traction.

But it's not only leaves on the line that cause delays.

There is something else that should never be only the line.

And that's us.

To give you an example, last year, not a single person was killed

whilst on a train,

but 20 people lost their lives by being accidently

hit by a train - and they were all trespassing on the railway lines.

As well as the loss of human life,

the effect on the network of such a tragedy is massive.

In January 2013, the cumulative delays caused by reports of

trespasses and collisions was a staggering 45 days.

When you analyse the data, the victims were trying to

retrieve a lost phone or wallet, they were taking a short cut,

and the vast majority were young males aged between 16 and 30

coming home after a late night on the weekend.

Now, bravado and alcohol play a role in those fatalities,

but for all the victims, there might be another factor at play

that you might find surprising - hearing.

If I was standing on a track, I would be able to hear a train

coming towards me, definitely.

It's echoey and loud. You're going to hear it. It's going fast.

I'd imagine I would hear a train...

Probably.

They tend to make a bit of noise,

and occasionally they sound a horn, don't they?

More than a third of us are convinced we'd be able

to hear a train coming soon enough to get out of the way.

But could we?

Scientists at the University of Salford are finding out how

fast people can react to a speeding train using an anechoic chamber.

So this is what an anechoic chamber looks like.

Nice to meet you.

So what are we going to do in here?

So we are testing people's ability to detect an oncoming train

when they are standing by a rail track.

-So I'm going to be your guinea pig.

-Yes.

-What do you need me to do?

I need you to sit on that chair over there.

All right.

In this completely silent space,

Dr Fazenda will recreate the sound a train makes as it passes.

The moment I hear it,

I have to press the keyboard to stop the train and then

identify its direction and speed...

-All right, Bruno, let's go for it.

-OK.

TRAIN APPROACHING

I think something was coming from the right.

TRAIN APPROACHING

-Slow.

-OK.

-TRAIN ON RAILS

-Left.

That was a fast train.

OK, so how did I do?

You missed one out of three

and unfortunately, one miss is one death.

-So I would be dead?

-Yes, on one occasion.

It's far more difficult that I would have imagined.

Even with no distractions, I still got one wrong.

How much harder would it be in the outside world?

What would happen if your hearing was impaired or muffled

because you were listening to music on headphones,

or had just been at a loud concert or bar?

The reason why sound can become muffled after being exposed

to loud music in a nightclub is

actually due to a protective mechanism within the ear.

Your ear is made up of the outer, middle and inner ear.

And the eardrum is connected to the inner ear by three little

bones that lever to allow the sounds to reach the inner ear.

Now when you are exposed to loud music,

the brain registers this loudness and signals to the muscles

attached to these little bones to tense up.

And so, the bones don't lever quite so much,

and minimise the amount of sound which reaches the inner ear.

-LOUD MUSIC AND MUFFLED SPEECH

-Now this is reversible - it's temporary hearing loss...

Now this is reversible - it's temporary hearing loss,

but it can last several hours depending on the length

of exposure and the loudness of the sound you have been exposed to.

Because we can't get our subject exposed to loud sound,

we filter the signals to emulate how we would hear the sound as

if they had been in a nightclub.

So it's going to be more muffled?

Yes.

But muffled hearing isn't the only factor at play here.

Another hazard is concentration.

In the first test, the train had my full attention.

But the reality is that much of the time we aren't

giving our surroundings our full attention because we are

listening to music, talking with friends or using our phones.

And I'm thinking, who would realistically

look at their phone when we are crossing the track?

But we are so used to hearing, "Beep-beep",

you are quite likely to whip it out and see who's been contacting you,

as you're doing something.

As I listen to the muffled sound, Dr Fazenda simulates this lack of

attention by having me read a book.

The book will give us the situation

where your attention is diverted into reading the book.

So you'll have to read a passage of this book out loud.

Out loud?!

Yes, so I know that you are actually paying attention,

and the task is still to tell me where the train is coming from.

I shall read the chapter on cake and carpentry.

That sounds very good.

"Whitstable is wonderful, the sort of place where Enid..."

Right.

Slowish, I think...

"The sort of place where Enid Blyton children still go to buy ginger pop

"and paper kites for a shilling..."

Whoa! That was a bit close.

Am I dead!?

"With shopping bags, off to buy

"a bit of haddock for his lordship's tea."

That was right and it was really fast.

-OK.

-How many times did I die on the tracks?

I'm afraid you have died twice.

Why? What did I get wrong?

Both of these trains sneaked up on you before you were able

to tell they were there.

And what is more interesting is that

-you are getting your sides wrong a lot more and the speeds.

-Really?!

So why did I get the direction wrong?

One of the things is because your hearing system

has been somewhat changed you are

missing out some of the frequency content which will give you a better

estimation of direction and that, of course, is one of the problems.

The other problem is that your attention is somewhere else,

so to estimate something that is a little bit more critical,

requires a bit more thought and you haven't got that cognitive

ability any more because you are focusing on something else.

It is shocking how dangerous this actually is from being distracted

a little bit from having been out in a loud place.

It's sobering.

Dr Fazenda has repeated this experiment with many

different subjects, and the results are always the same.

It all adds up - the way sound emanates from trains,

listening to loud music, distractions,

they are all a recipe for disaster

when it comes to accidents on rail tracks.

Let's face it,

there are only two places you should be on the railway -

safely on the platform or on the train.

Even with Crossrail and possibly HS2 coming on stream in the future,

our existing system will continue to be put under huge pressure

as passenger number increases.

The one thing we do know is that

passenger numbers are set to increase,

but with the right investment and the right technology,

the trains will run on time, most of the time.

Next week, Bang is asking if science can offer any relief

as the refugee crisis in Syria worsens...

In the meantime, to find

out about careers in the railways check out the website at /bang.

And to find out more about the science of rail,

follow the links to the Open University's interactive pages.