Original subtitles

ANNOUNCER: This program is rated PG, and contains

ANNOUNCER: This program is rated PG, and contains

ANNOUNCER: This program is rated PG, and contains

mature subject matter.

Viewer discretion is advised.

(TRAIN DRIVER SPEAKING SPANISH)

NARRATOR: One of the worst train crashes in Europe's history.

There is people screaming, there is kids screaming.

BOBBY: There's mothers screaming out for their kids...

NARRATOR: But what caused this catastrophe?

Something must've gone really wrong for this train to crash in this way.

(SIREN BLARING)

NARRATOR: Now.

Engineers unlock the clues to the world's biggest disasters...

(UPBEAT INSTRUMENTAL MUSIC PLAYING)

(WOMAN SCREAMING)

NARRATOR: To find out what happens when big things go wrong?

(MAN SPEAKING INDISTINCTLY)

These are ultimate fears that keep structural engineers awake at nights.

MAN: Oh, my God!

NARRATOR: It's 8:31 p.m. on a summer evening in rural Spain.

The latest in high-tech transport, the S730 train is speeding north

towards Santiago de Compostela.

The S730 is built to bring high-speed travel

to areas of Spain that haven't had it before.

Particularly this area that's furthest away

from the capital city Madrid.

NARRATOR: This train is built for speed.

The S730 is one of the newest designs on the rails

and has been in service for a year.

ROB: It offers luxury with lightning pace.

NARRATOR: The train contains 11 pressure-sealed passenger rail cars.

And can transport nearly 300 people.

Onboard the packed train today are 218 passengers,

including Texan, Bobby Fariza and his wife Myrta.

I'm there all excited because I love high-speed trains.

NARRATOR: For them, it's the vacation of a lifetime.

On their itinerary, a Spanish festival.

BOBBY: In Santiago de Compostela,

they have what they call the Fiestas Patrias.

It's a very big party. You got over a million people

coming over for a span of about ten days.

The fireworks are incredible.

And I was excited because I wanted my wife, Myrta, to see it.

NARRATOR: But what the Farizas don't know

is they're moments from disaster.

As it closes in on its final destination,

the train is travelling at 120 miles per hour.

The train is hauling and is going through

a series of different tunnels.

NARRATOR: It's a section the drivers navigated countless times before.

As it exits the tunnel, there's a sharp bend.

(DRIVER SPEAKING SPANISH)

NARRATOR: Drivers have warned officials about this notorious corner.

Trains must slow down to 50 mph to drive through it safely.

The train tilts to the side, like that,

when it's going through a curve, whichever side it's going.

NARRATOR: But today the train doesn't stop tilting.

All of a sudden it just kept turning and turning.

Everything and everybody that was on this side of the train

was starting to fall on our side.

And very violently just went on its side.

(PASSENGERS SCREAMING)

That's when everything went black and white.

(TRAIN HORN TOOTING)

The train goes around the curve,

we see the first car makes it all the way around,

but then weird things begin to happen.

If you're in the back, you might have heard something

for like a second right before you got thrown.

A loud bang, or a series of loud bangs.

Lights go out, it's probably like a bomb went off.

(CRASHES)

NARRATOR: The train is now scattered

across hundreds of feet of track...

A diesel generator car is on fire.

Rescue won't be easy.

Bystanders and emergency services begin a desperate race

against the clock, to rescue survivors trapped in the crushed wreckage.

It's carnage everywhere. The trains have ripped open,

people have been thrown out everywhere.

Seventy nine people are dead,

and almost everyone else is injured.

NARRATOR: The crash is devastating news.

The derailment or crash of a high-speed train in engineering terms

is a very surprising thing to occur,

high-speed train travel is renowned as being

one of the safest modes of travel in Europe.

So when a high-speed train in particular crashes,

everybody really sits up and takes notice.

NARRATOR: What causes this state of the art train to crash

with such heavy loss of life?

Answers to this mystery begin back in 1990.

Spain is getting ready to host the Olympic games and a major world expo.

So it's a really big year

as Spain really arrives again on the world stage.

NARRATOR: Thousands of visitors need to move around the country and fast.

Solution? Build a modern high-speed electric rail network

with 2000 miles of track,

enough to stretch from New York to Utah.

The Spanish Government have made the decision to invest heavily

in these new high-speed lines,

because new infrastructure is going to bring in more business,

more tourism to the area's economy.

NARRATOR: The price tag... a hefty $72 billion!

Technology and building materials are key

to the high-speed train revolution.

They also hold the first clue to why this crash is so deadly.

The first new train model to hit the tracks is the S130 in 2007.

Designing a high-speed train

isn't like throwing together a slow brick shaped Amtrak,

it needs to be aerodynamic,

and to go as quickly as possible it also needs to be light.

NARRATOR: Its aerodynamic nose

is designed to reduce air resistance.

ROB: Some high-speed trains, like the S130,

are built like an airplane on rails

using specialist materials like aluminum

to keep the weight down.

NARRATOR: Aluminum is three times lighter than steel.

Helping trains reach an incredible 155mph.

Twice the speed of older models.

DAN: In many ways, thinking of a high-speed train

is like thinking about an airplane.

You have an aluminum tube full of human beings.

That tube is lightweight and designed for efficiency,

but not for crashworthiness.

NARRATOR: But there's an issue.

Aluminum isn't as strong as steel.

So, when a crash does occur usually it's really, really bad news for people on board.

I mean, think about taking an aluminum can

and throwing it at a wall made out of concrete,

the can is definitely going to lose.

NARRATOR: And when the Spanish train derails,

that metal is all that protects its passengers.

Making the wrong choice in material can be disastrous.

A lesson learned on US Speedways in the late 1960s.

IndyCar racing. The ultimate combination of man and machine.

And its fans are growing.

NARRATOR: Designers need new components to build winning cars.

New materials meant IndyCar's could go faster than ever.

And accelerate at shocking speeds.

NARRATOR: And the material they turn to... aluminum.

The cars became lighter and would move faster down the track.

So new speed records were being made.

MAN: With an average of 147 miles an hour, a new record time...

NARRATOR: But as speeds increase, so does the danger.

MAN: The track is filled with flying wheels and other auto parts.

Setting off the worst chain reaction accident in Indianapolis history.

SIAN: The thing about aluminum is it's super lightweight,

but it's not really resistant to breakage,

and so it's great when you wanna go fast,

but it's terrible if anything goes wrong.

MAN: The red flags are out and the track is alive

with firemen, ambulances, officials and pit crews.

When cars would crash, these new materials weren't as strong,

and there were some very, very serious accidents back in those days.

NARRATOR: During the '60s and '70s,

fifteen drivers die in these lightweight cars.

MAN: Dave MacDonald loses control of his juggernaut and spins into the wall.

It starts a chain reaction as others pile up.

Seven cars are involved.

Eddie Sachs smashes into MacDonald and askew.

MacDonald dies later in the hospital.

NARRATOR: Then, in the 1980s, engineers find

a safer alternative, carbon fiber.

Deaths fall by 87 percent.

In the Spanish train crash, aluminum coaches crumple like tin cans.

Which helps explain the high death toll,

one third of the passengers lose their lives.

But why does the train fly off the tracks in the first place?

Coming up...

More pieces to the puzzle uncovered.

ROB: You have to have the weight in the right place at the right time.

And if it isn't, you are in for a whole lot of trouble.

NARRATOR: And later, a 747 tragedy shows what happens

when big things... lose their center of gravity.

(DISTANT EXPLOSION)

NARRATOR: When big things go wrong,

engineers have to find out why.

In the Spanish train wreck,

building cars from lightweight metal proves fatal.

Aluminum is not designed for crashworthiness.

It's actually designed for fuel efficiency and high-speed.

So, if their crash does happen with those particular vehicles,

it's really, really bad news for the people on board.

NARRATOR: But aluminum didn't cause the accident, so what else did?

By 2012, Spain's high-speed rail revolution is proving

so effective that more regions want to be a part of it.

The availability of a high-speed rail network

covering all of Spain increases accessibility

for passengers and generates competition for both road and air traffic.

NARRATOR: But these remote areas have old track that's not electrified.

And new high-speed trains can't run on it.

There's the current situation where you've got both

new electrified track and older non electrified track.

And to electrify the whole country

will take a lot of money and a lot of time.

NARRATOR: It's an expensive problem.

But there's an easy solution.

Change the trains, so they can run on both types of track.

What they did was add two diesel engines to an S-130

in order for it to generate its own electricity,

and to be able go to the places they couldn't go before.

NARRATOR: A new hybrid train is born.

Renamed the S730, it generates its own power when it needs to.

ASEGAN: It's similar to, like, a plug-in

extended range hybrid like a car,

in the sense that it can plug into the track, so to speak,

get its electricity from the track and that can drive it,

which essentially is being driven by a power plant, which is elsewhere.

Or you can drive with its own onboard engine.

NARRATOR: This lets the S730 high-speed train travel anywhere in Spain.

This versatility makes it the toast

of the Spanish railway industry.

NARRATOR: But there's an issue.

This new train develops a reputation amongst its drivers.

They refer to it as the Frankenstein

or a train that's been cobbled together

from different pieces,

if you think of the old monster with scars and bolts

coming out of its neck...

It's not a compliment.

NARRATOR: Adding two diesel generators means extra weight.

Over 158,000 pounds per train.

ROB: The extra weight that's been built into these trains isn't a problem per se.

But the fact that

these great hunky diesel generators

sit higher up in the cars

means that the center of gravity

of those carriages has now been raised.

This new train's specifications says that it shouldn't be

more than 40 tons heavier than the original train.

But it's actually 72 tons heavier,

and this makes a big difference when you're going fast.

NARRATOR: It's a dangerous design choice.

The problem with having a higher center of gravity for a rail car

is that it becomes less stable around the corner.

It's easier to tip over.

And that is the consequence of adding a diesel generator car

to the S130 high-speed train.

You have to have the weight in the right place at the right time.

And if it isn't, you are in for a whole lot of trouble.

NARRATOR: A shift to the center of gravity can cause serious trouble.

As one crew discovers at a US airbase in Afghanistan.

April, 2013.

Bagram air base.

A cargo plane carrying military vehicles takes off.

Every plane that takes off is finely tuned to have perfect weight and balance.

This is why your luggage is weighed

every time you go to the airport.

NARRATOR: All seven crew die in the crash.

This 747 is fully loaded.

It's carrying five armored vehicles.

Each weighing 40,000 pounds.

This kind of cargo must be evenly distributed and secured.

What now happens is if a strap breaks

that was used to hold these things in place,

the weight just shifted around inside the plane.

When that weight shifted to the back,

it's going to change the balance inside

and cause it to tip backwards.

SIAN: Once this shift in weight happens,

there was nothing the crew could do.

It's a series of events

that all go wrong.

It starts with something really small,

you know, a strap or harness

which ultimately just comes down to some guy hooking it up.

And it doesn't work... and the whole thing goes down.

(DISTANT EXPLOSION)

-NARRATOR: Coming up. - (SIREN WAILING)

More clues are revealed.

When trains are moving at really, really high-speed,

the relationship between that speed and the human reaction time

becomes a very, very important component in operating a train safely.

NARRATOR: And a cruise ship is on a collision course.

-MAN: Hold on, hold on! -WOMAN: Hold on!

NARRATOR: Trains are some of the fastest and largest machines on Earth.

So when they go wrong, the results can be catastrophic.

They crash for all kinds of reasons.

Mechanical failure.

Foreign objects.

MAN: Oh, my goodness!

NARRATOR: And driver error.

As in this deadly crash in Los Angeles.

Even still, it's one of the most reliable modes of transportation.

(CRASHES)

So the Spanish high-speed train derailment is baffling.

DAN: Statistically it's much safer to travel

via rail, or train, than it is in a car.

This is the question, why did this happen to this particular train?

NARRATOR: The train has a lightweight body

and it's Frankenstein design makes it unstable.

But these only become a problem when it travels too fast.

(HORN TOOTING)

NARRATOR: Was that the case here?

1992, Spain's new trains are designed to travel

at 155mph on straight tracks.

But in parts of the country, straight routes are impossible.

The area of Galicia that this train line has been built in

is incredibly mountainous and rugged.

And so engineering a straight flat rail line

for tens of kilometers to allow a high-speed track

is an extraordinary civil engineering challenge.

And in the end, they end up having to build 31 tunnels

and 38 sections of viaduct in order to get the track across this countryside.

NARRATOR: When trains approach Santiago, they must slow down

to 50mph to navigate the very sharp corner.

If the driver gets it wrong, they're in trouble.

When trains are moving at really, really high-speed,

the relationship between that speed and the human reaction time

becomes a very, very important component in operating a train safely.

There's just less time to react to dangerous situations,

but the driver has to do it in order for the train to be safe.

It's a very, very high pressure

and very demanding job environment.

NARRATOR: Records show that on the night of the crash,

the train approaches the corner at 121 mph.

(TRAIN HORN TOOTING)

With the last warning sign

is just 500 feet before the bend.

There's simply not enough time to react.

Even if you do react quickly, it's gonna take a long time for your reaction

to manifest in what the train then does.

Even though we consider these to be lightweight trains,

these trains still weigh many, many, many tons.

So to stop such a massive vehicle in a short amount of time is very difficult.

You need a significant amount of time and warning to go

from a hundred miles an hour to zero miles an hour.

It doesn't happen in a blink of an eye.

NARRATOR: Something all too familiar to one cruise liner captain.

Venice, Italy. A regular stop-off for cruise ships.

Including some of the biggest on the seas.

ROB: The MSC opera is an enormous cruise ship,

it's 902 feet long, and weighs over 65000 tons.

That's the equivalent of ten Eiffel towers.

NARRATOR: Venice's ancient sea-lanes are a tight squeeze.

The ship's been built with a plethora of safety features.

She has state of the art navigation and forecasting equipment.

And the crew and the captain have been here hundred of times before.

This should be a routine situation.

NARRATOR: The captain must get the approach speed just right.

But this cruise ship doesn't slow down.

(INTENSE MUSIC PLAYING)

(SHIP HORN TOOTING)

(MAN SPEAKING)

(LOUD CRASH)

As the MSC Opera is approaching Venice,

there's a problem with the engine.

And rather than the engine turning off,

the throttle is turned on full thrust.

This is a known problem on ships that's not all that uncommon,

but it usually happens way out at sea

where there is a chance to react.

Nearer to the land... this becomes a massive issue.

NARRATOR: The crew makes a final attempt to slow the ship.

Two tugboats try to guide the ship away from danger,

but one of the steel cables snaps.

The pilot deploys both of the MSC Opera's anchors to try and slow the ship.

But it has very little effect.

It's still moving at speed.

NARRATOR: It's now unstoppable.

(MAN AND WOMAN SPEAKING)

This is a boat that's 14 decks high

coming at you at full tilt as you're stood on the dock.

And clearly your only instinct is gonna be to get out of the way

as quickly as you can.

Even when it hits solid ground, the ship keeps moving.

65,000 tons of inertia refusing to stop,

until it finally grinds to a halt.

NARRATOR: People run for their lives

as The MSC Opera slams into the city.

(MAN SPEAKING)

(WOMAN SPEAKING)

NARRATOR: Five are injured.

The damage runs to hundreds of thousands of dollars.

But everyone involved escapes with their lives.

Passengers on the Spanish high-speed train...

aren't so lucky.

Coming up...

Was this tragedy just due down to driver error,

or could a new clue reveal

why the train is travelling so fast?

To switch that system off and still run it at high-speed

is absolute insanity.

And a Gulf of Mexico oil-platform shows how failsafe systems...

don't always work.

This ended up being the worst oil spill

in the history of humanity.

NARRATOR: Big disasters can have an obvious cause.

But sometimes finding answers is more complicated.

Especially in a high-speed rail crash.

In the aftermath of the crash,

you have considerable destruction,

you have rail cars leaning over on their sides,

some of them turned upside down.

One car, which is essentially stood on end,

leaning up against a concrete retaining wall.

High-speed trains like this are not supposed to crash.

They are designed to have some of the safest technology available.

NARRATOR: So what happened to the safety systems on the Spanish trains?

Spain's new high-tech trains are designed with computerized safety systems.

Basically an electronic system that constantly monitors

where a train is at any one time.

How fast it's going, and what's coming up ahead.

NARRATOR: And crucially, there's an automated brake.

If the train's going too fast, this system should slow it down.

This is very much akin to what they're starting to put in cars now,

which are also emergency auto-braking systems,

where if you're driving,

you're too close to the car in front of you,

that car stops, um, not only does it alert you,

but it also can stop the car itself.

A system like this could save lives.

NARRATOR: So accidents caused by human error should be impossible.

But after just a week in operation, the S730 has a hiccup.

There are malfunctions with the automatic braking system,

and the error causes trains to come to a halt.

NARRATOR: When trains switch from new track to old,

the automatic brake kicks in even at safe speeds,

causing delays that cost money.

So now a decision is made to turn off the automatic safety braking system

on this particular model of train in this particular section of line.

NARRATOR: Now, monitoring speed is all on the driver.

You absolutely need a failsafe system that acts as a safety net

to catch any mistakes the driver might make.

To switch that system off and still run it at high-speed is absolute insanity.

NARRATOR: It's a recipe for trouble.

A working failsafe is crucial in any complex machinery.

As the crew on a mega drilling rig in the Gulf of Mexico experienced.

Drilling into a pocket containing over a million gallons of crude oil.

This is one of the most complex machines on the planet.

It's extremely dangerous because what makes things explode is pressure, right?

And at the same time, the thing that's at high pressure is combustible.

NARRATOR: But on April 20th 2010, the unthinkable happens.

(FIRE CRACKLING)

Just hours before, the crew perform routine maintenance.

Capping a freshly drilled well with concrete.

This is standard procedure

to cap it off, so it doesn't leak oil

or anything else into the sea.

They do a pressure test

to determine if the concrete is holding and they completely misinterpret the results.

They think everything's fine,

but they couldn't be further from the truth.

NARRATOR: A surge of natural gas and oil

blasts through the concrete seal.

Engineers activate the rig's failsafe system,

the blow-out preventer.

A mechanism designed to close the pipe.

You had these safety systems,

they're supposed to be able to kick in and cut the pipe,

shut it down, turn it off and none of them worked.

NARRATOR: Natural gas shoots up the drill, and ignites.

(FIRE CRACKLING)

Eleven die in the blast.

The 300 foot flames can be seen from 35 miles away.

And 4.9 million barrels worth of crude oil

leaks into the Gulf of Mexico.

I mean, this ended up being the worst oil spill in the history of humanity.

NEWSREADER: The well maybe capped,

but the oil is still gushing out of control.

A torrent of crude soaking Louisiana's coastline...

creeping all the way to Florida.

Now the lesson from Deepwater Horizon for us is that

we can't rely purely on technological solutions to ensure failsafe.

And neither can we rely purely on humans

to make the decisions that are gonna give us our failsafe.

We have to use them in harmony with one another.

NARRATOR: Coming up...

With the fail safes disabled, this high-speed train is left vulnerable.

The driver suddenly realizes where he is

and hits the emergency breaks,

but it's too late.

NARRATOR: When big things go wrong the results can be devastating.

-(PEOPLE SCREAMING) -Bridges collapse.

Ships sink... and planes fall out of the sky.

(PEOPLE SCREAMING INDISTINCTLY)

NARRATOR: But for people involved in these tragedies,

the day often begins like any other.

The 04155, a hybrid high-speed train is about to leave

the Spanish capital, Madrid.

218 passengers are boarding...

including Texan, Bobby Fariza and his wife Myrta.

Here comes the train and, so we get in.

The train was so packed.

We sit down, all excited with the train ride,

and, and the train just runs smoothly.

As we go along, we eat a little, go to the cafeteria.

Keep watching our suitcases because they're all the way up there in the front.

And, uh, just enjoying it.

NARRATOR: The train reaches its top speed

as it cuts through the Spanish countryside.

It heads through a series of 31 tunnels.

Imagine going down this line

where you alternate tunnel to bridge, to tunnel to bridge,

and the only thing that you have as a driver

to keep track of where you are is visual cues.

They had announced that we are arriving to the train station.

Um, my wife, she then, um, says to me,

"Oh, Bobby, I bet you, you want to go straight to the door knowing you."

And so it was one of those, "Okay, honey. Yes, honey."

So, I sat down, I did not go to the door.

NARRATOR: At this point,

the driver needs to start slowing the train down

from its current speed

of 120mph to navigate the dangerous corner.

If the driver hasn't started braking four kilometers before he gets to the curve,

he isn't gonna get around safely.

NARRATOR: But at the worst possible moment...

The phone rings.

(INDISTINCT CHATTER)

Now, the idea that they could take phone calls and all these things,

in the midst of that is, like, really a recipe for disaster.

Particularly when you got a section

of the route where, like, it hinges

on the driver actually slowing the train down.

It seems utterly utterly, utterly incomprehensible

that someone would be phoning the train driver

as they are approaching this curve which is known to be dangerous.

NARRATOR: The train heads down a short slope, picking up speed.

BOBBY: My wife, she then says to me

if there's anything that she needs to carry?

So I pick up, I went ahead and I'm picking up my backpack.

NARRATOR: The train approaches the final tunnel before reaching Santiago.

After spending over a minute on the phone the driver hangs up.

(TRAIN DRIVER SPEAKING SPANISH)

You got to imagine, you're travelling at a high rate of speed

and you're looking for landmarks.

So the moment you take your eyes away,

even to pick up a phone,

by the time you look back up,

your scenery has changed.

And for you to be able to recognize that, is not easy.

NARRATOR: The train exits the last tunnel

and speeds past the final warning sign

of the approaching corner.

The driver suddenly realizes exactly where he is on the track.

Just a few hundred meters away from the corner.

He throws down his phone

and slams on the emergency brakes.

NARRATOR: But it's too late.

(LOUD CRASH)

That's when everything went black and white.

And I, in my corner of my eye, my wife was still there.

And then all of a sudden I could see her go like this.

Um, she hits with her head on the little table

that's in the back of the seat.

I had, you know, a feeling that this was not gonna be good.

And that's it. I was knocked out.

(HORN TOOTING)

NARRATOR: In just a few seconds, the train derails,

trapping passengers inside.

Still in shock, the driver calls for help.

(TRAIN DRIVER SPEAKING SPANISH)

(SIREN WAILING)

I wake up, and I look around, I'm thrown on the floor.

I feel a lot of pain in my back,

and a lot of pain on my hips, my knees,

and especially on my hip, on my right side.

But with all the energy and of course all the adrenaline,

I realized that I could stand up.

That's when I get to see the whole scene.

It is just like a scene from Hollywood.

You've got train crashes all bent up.

There is people thrown on the floor, all bangled up.

There's people screaming, there's kids screaming,

there's mothers screaming out for their kids.

I'm yelling out for my wife.

All I could hear was this one guy,

he's screaming out for his mom,

and he has an ear hanging out.

We are the only two in there

that actually got up out of the 40 something people

that were in that in that car.

A lot of people from the neighborhood came inside

and started pulling out people, and started to help.

They started pulling out my wife...

She was conscious. I could see that she was not doing too well.

We pray together, the Lord's prayer.

She couldn't say it, but she was holding on.

And every time would squeeze my hand...

(STUTTERS) as I said the Lord's prayer.

NARRATOR: Bobby's wife Myrta dies.

The crash takes a grim toll.

Everyone onboard is injured or dead.

It's like, all the wrong things coming together

at the right moment.

(SIREN WAILING)

(MAN SPEAKING SPANISH)

NARRATOR: In Spain, Engineering compromises

and bad decisions have led

to one of the worst railway disasters in its history.

A high-speed train packed with 218 passengers has derailed,

slamming into a concrete wall.

Seventy-nine die.

It shocks the world.

But seen through the eyes of modern engineers, it's not a surprise.

This tragedy would have happened one way or the other.

There were just too many deficiencies in the system

to allow it to operate safely.

NARRATOR: Aluminum that crumples in the crash.

Lightweight materials just aren't as tough when things go wrong.

NARRATOR: The train travelling too fast.

Being a high-speed train driver, getting a phone call right at a critical moment

when you need to be paying attention.

NARRATOR: Extra weight from the diesel generator cars

throws off the train's balance.

It becomes less stable around a corner. It's easier to tip over.

NARRATOR: A safety system fall back is switched off.

It's really inconceivable to me that anyone would turn off

the automatic braking system intentionally.

and leave the only protection of the train and its occupants to the single driver.

That is just shocking.

It's like this combination of human error and design error.

NARRATOR: But what happens in the final moments

as the train approaches the corner?

(LOUD CRASH)

It starts with the tiniest clue that something is not quite right.

The floor starts wobbling...

as forces it's not designed to take start coursing through its metal shell.

The first car to derail is the top heavy diesel generators.

They drag the rest of the train off

causing this accordion like destructive event.

And then all hell breaks loose.

The driver car at the very front, he doesn't have most of the mass,

the mass is right behind him,

and so as he goes around the curve,

the big mass behind him yanks everything else

and slings it up against the side wall.

SIAN: The cars they crash into each other,

piling up and splitting open.

We can see the violence and all the kinetic energy

that is trapped in this train being released as the debris goes everywhere.

Order turns to chaos,

the forces take over,

the cars are now projectiles flying through the air.

NARRATOR: For Texan Bobby Fariza,

will never forget that moment.

This is in the car that we were in. Car number 7.

And, uh... My wife and I were sitting on this side, here.

And, uh, everything that's on this side of the picture went over to our side

when the car flipped over on its side.

NARRATOR: In the end,

the train driver is held to blame for the crash.

For victims, there is no consolation.

BOBBY: We were college sweethearts.

I miss her incredibly.

The loneliness without my wife is incredible.

That is something that I had to learn how to deal with,

and start a whole new life

without having her.

It's not that easy.

NARRATOR: In the immediate aftermath,

Spain reinstates the automatic braking system.

And around the world, high-speed rail services make changes,

including in the US.

The Acela Express that's been running for two decades

between Washington DC and Boston,

has the fastest trains in America

with speeds up to 220mph.

NARRATOR: After several high profile derailments,

Amtrak and other local rail systems

are making safety an even greater priority.

Among their efforts, installing smart energy braking systems

to detect changes in track layout

and monitor rail traffic.

Ride on this train and there's backup technology

to prevent an accident happening in the first place.

And in my opinion

that's exactly how it should be.

NARRATOR: Every time a big thing goes wrong,

engineers learn from mistakes.

To build smarter, faster and stronger.

(INDISTINCT CHATTER)

MAN: Oh, my God!

(CRASHING)