♪ ♪ ♪ ♪ (radio chirps) MAN: Okay, track is live.

Cars on the move in five, four, three, two, one.

Action all vehicles.

(engines revving, tires squealing) TITO: What the hell's that?

LYNN: Whoa!

LUKE: Oh, my God!

♪ ♪ (tires skidding) (car horns blaring) NARRATOR: A team of automotive experts has just staged an extraordinary experiment.

Look at your Porsche.

Was that meant to happen?

NARRATOR: A multi-vehicle highway pileup, using remote-controlled cars driven by volunteers who are unaware of the experiment's full objectives.

(clucks tongue, sighs): Just, what is going on?

NARRATOR: Had this been a real highway crash, what would have happened to the drivers and the passengers?

That's going to be a severe head trauma.

NARRATOR: Which cars made it through?

JANET BAHOUTH: So assuming everybody's belted, I think this person's probably walking away.

NARRATOR: And which didn't?

LYNN: Oh, I'm just thinking, if I had the grandkids in the back.

NARRATOR: And can crash forensic experts who did not witness the pileup... ANDY SHELTON: The mantra in forensics is, every contact leaves a trace.

NARRATOR: ...decipher the aftermath of the wreckage to discover the truth of what happened?

TITO: Oh, my goodness, man.

Yeah.

NARRATOR: "Ultimate Crash Test: Impact."

Right now, on "NOVA."

(tires skidding) Oh.

Oh!

Oh, my God!

♪ ♪ ♪ ♪ (engines humming) (radio chirps) (speakers echoing in distance) Okay, track is live.

Cars on the move in five, four, three, two, one.

Action all vehicles.

NARRATOR: After years of planning, a team of automotive experts has achieved something extraordinary.

Successfully executing a controlled multi-car pileup.

Bloody hell, the Porsche is off.

Blimey, everyone's steaming away.

(chuckles): I know, look at 'em go.

NARRATOR: Eight real vehicles driven by remote control from specially adapted compact cars.

(radio chirps) 800 meters.

Very good, keep in your lane.

NARRATOR: Four of the remote drivers had no idea their vehicles were about to be involved in a huge accident.

600 meters.

NARRATOR: While the other four were there to make sure they were.

200 meters out.

NARRATOR: At a predesignated moment, a remote-controlled truck crossed into their lane.

TITO: What the hell's that?

NARRATOR: A crash made even more unavoidable by a layer of gravel designed to mimic icy roads and poor-visibility weather conditions.

LYNN: Whoa!

CAITLAN: I can't see!

NARRATOR: What can be learned from this chaos?

Oh.

Ooh!

Jesus!

♪ ♪ (tires skidding) TITO: What?

Oh, my goodness!

LYNN: Oh!

(tires skidding) (tires skidding) (car horn honking) CAITLAN: I've just crashed!

(laughing): My God!

(car alarm blaring) ♪ ♪ JAMES BRIGHTON: Drivers, there has been an accident on track.

No cause for alarm.

Everybody is safe.

We will now investigate.

TITO: What?

Was that for real, or was that A.I.?

Has Caitlan's car gone underneath the truck?

(breathes deeply) Deep breaths, Caitlan, deep breaths.

(siren blaring) NARRATOR: The team has completed the first stage of the experiment, a multi-car pileup, with no injuries, every detail painstakingly recorded from start to finish.

♪ ♪ (radio chirps) BRIGHTON: JLB team, please kill cars, over.

NARRATOR: Team leader James Brighton is now ready to begin the next phase of the experiment: analyzing the incredible footage, vast quantities of data, crash scene, and witness accounts before the cars are sent back to Cranfield University, the team's base, where they'll be further analyzed by automotive engineering students.

♪ ♪ After years of preparation, it's a huge relief to see all the pieces finally come together.

(laughs): This is so great.

So cool.

NARRATOR: Helping to dissect the pileup is crash analysis expert Janet Bahouth.

BRIGHTON: So the Golf made it through?

BAHOUTH: Yeah, it... BRIGHTON: Ah, no way.

BAHOUTH: It clipped the back end, yeah.

BRIGHTON: Wow.

NARRATOR: For Janet, this wreckage site has extraordinary potential.

Normally, she only gets to see the aftermath of a real-life crash.

But this crash is different.

Each vehicle was equipped with black boxes that captured every detail of the event, including speed, impact force, and brake pressure.

Plus, with more than 90 cameras recording the entire incident, Janet and her team will have a 360-degree view of how the scene unfolded.

I'll tell you what, this is the coolest thing ever.

(laughing) So neat to see this, and to have a video of it the entire way through is fantastic.

♪ ♪ NARRATOR: Although it's rare for cars to catch fire in crashes, the fire crew makes sure the site is safe.

♪ ♪ Back at the pod enclosure, the four volunteer drivers, Tito, Caitlan, Luke, and Lynn, are still processing what just happened.

I saw Luke slow down.

I was, like, "Oh, I, I bet...

I got to slow down."

Oh, my God, I'm so confused.

NARRATOR: They were selected to represent different ages and driving styles.

None of them knew they were about to be involved in a multi-car pileup.

Before taking part, they all underwent psychological screening to make sure they could cope with the emotional toll of being involved in the crash, and will now be assessed again by a psychologist.

None of these assessments are filmed, in order to protect the drivers' privacy and well-being.

The other four drivers, Mark, Aisha, Pete, and Chenhui are part of James's team, and knew exactly what was coming.

Hi, everybody.

NARRATOR: All four of the volunteer drivers are given the all-clear.

And they all want to learn more about the experiment and see the crash site up close.

BAHOUTH: So what we have here and what all of these people have put together was done on purpose.

(chuckling): And we thank you for being a part of this.

We used you as the drivers who didn't know what was going on.

And my job in all of this is to look at how you fared in your vehicle.

Thank God you weren't actually in it.

(others murmuring agreement) We have, in our world, we have crash tests where it's all very sanitized and instrumented, and we know exactly what's going to happen, for the most part, before it does.

In the real world, of course, we have no idea.

What we did is, we mixed the two worlds.

(chuckling) A lot of naysayers about how this was never gonna work.

MAN: Mm-hmm.

We did it!

We did it!

Thank you!

(others exclaiming) BAHOUTH: You were a huge part of this.

(Tito exclaiming) ♪ ♪ NARRATOR: Not one car escaped the pileup without damage.

Some are almost unscathed.

Others are barely recognizable.

One element of it that we really didn't want is just one enormous pileup, where there is no decision to be made by the drivers.

There's really very little to learn.

Every driver took a different reaction to the events that were unfolding in front of them.

♪ ♪ NARRATOR: In the real world, every major pileup is carefully investigated to determine what happened.

This staged crash is no different.

A team of crash investigators will now analyze the incident using standard forensic techniques.

To keep the investigation as realistic as possible, the forensic team has been sequestered.

They did not witness the crash and have no prior information.

Leading the crash forensic team is former U.S. state trooper Andy Shelton.

SHELTON: So, I'm going in blind, um, and I'll approach this crash as I would any other.

Uh, I'll work my way to the center of the chaos and try and, uh, travel the paths back outward until I can figure out, uh, some idea of what's going on and hopefully be able to, uh, give you a cogent report at the end of it.

NARRATOR: Andy spent more than 20 years with the Tennessee Highway Patrol, including time with their Critical Incident Response Team, where he responded to hundreds of incidents.

But he's never investigated a pileup that's been captured in minute detail by so many cameras.

This unique opportunity is a chance to put traditional crash investigation techniques to the test.

SHELTON: The challenge is, you have the disorder or the chaos of the crash scene, but you have to be able to make order out of it.

The mantra in forensics is, every contact leaves a trace.

Uh, we're able to use that to figure out how they came into the crash and, and, ultimately, what caused it.

NARRATOR: For the investigation, Andy is pairing up with Marcus Rowe, a former U.K. police forensic collision investigator.

He, too, saw nothing of the accident.

ROWE: I always wanted to be somebody's lackey.

NARRATOR: Their first job is to scan and model the entire scene in 3D using lidar.

Yeah, now you got line of sight there.

♪ ♪ NARRATOR: Lidar technology allows investigations to continue long after the wreckage has been removed and roads reopened.

SHELTON: So we're gonna be able to take the scene that we have here and drop it back on to, for instance, Google Earth or something like that.

If this were to be a criminal case, we can show the context of the roadway around it.

Uh, things like line-of-sight issues, hills, trees, anything that may have distracted a driver along the way.

Okay, that's good.

NARRATOR: With the entire crash scene scanned, the forensic investigation begins.

SHELTON: So you can see the pulsing from the A.B.S.

on the, on the roadway.

And if you look here, Marcus, there's some scuffing here.

And then we've got the flat tire scuff from the left front tire.

NARRATOR: As in the real world, the challenge for the crash investigators is to try and figure out how the pileup unfolded.

SHELTON: So this could be undercarriage of the Audi.

ROWE: Yeah, but... Trailer's like this.

NARRATOR: Janet, who knows exactly how the crash played out, will be able to judge how accurate their conclusions are.

Those marks are to the far-side tires.

ROWE: We're looking for the, the physical evidence that talks to us, right?

That tells us the story.

That can only be made in one way.

♪ ♪ NARRATOR: As Andy and Marcus work to pick apart the crash details, Janet can now show the drivers how their actions in the pods played out on the track, and whether the safety systems in their cars would have done enough to protect them.

First up is Lynn and her Prius.

Lynn was driving at the rear of the pack, with team driver Pete following closely behind in the white van.

From her position, she is able to spot a problem ahead and quickly brings her Prius to a stop.

LYNN: Whoa.

(tires skid, vehicles collide) Whoa!

What's bloody happened there?

Oh, God.

NARRATOR: Pete, traveling below the speed limit, at 62 miles per hour, plays the role of a distracted driver and crashes into the back of her car.

♪ ♪ LYNN: Oh, God.

And I thought I was safe.

I didn't realize that had happened.

Oh, my God.

Oh, crying out loud.

I didn't think I'd feel like this, that it's not real.

But it could have been.

Oh!

Yeah.

NARRATOR: Despite the Prius being rear-ended, a built-in safety feature called a crumple zone took the brunt of the damage.

Crumple zones are designed to deform under loading so that other areas of the vehicle are better protected in a crash.

You're transferring less crash energy to the occupants, and therefore you're reducing the injury risk.

♪ ♪ Would my grandkids have survived?

Oh, for crying out loud.

BAHOUTH: Let's go take a look.

NARRATOR: Data from the on-board crash recorders registered an impact of 22.5 G when the Prius was rear-ended by the van.

LYNN: Whoa!

What's bloody happened there?

Oh, God.

NARRATOR: To put that in context, astronauts experience up to 4 G during takeoff.

THOMAS: The goal is always to keep the occupant cabin intact.

And so you want to dissipate those crash energies elsewhere in the vehicle.

This helps to reduce damage to these important areas of the vehicle that could lead to things like fires or leaks or other failures.

This is what's underneath-- this is... NARRATOR: Crumple zones are designed to absorb forces of around 20 G. (device beeping) The 22.5 G impact has totally crushed the trunk space and led to a deformation of the rear cabin.

LYNN: What injuries would I have sustained, do you think?

So, it's hard to say, but I think you might have some bruising, abdominal bruising, from the seat belt.

LYNN: Oh.

BAHOUTH: Um...

Probably some neck pain, at the very least.

Yeah.

Um, I'm a little bit more worried about somebody in the back... LYNN: Oh, don't say that!

BAHOUTH: ...because they were directly impacted.

(gasping) NARRATOR: The rear of the car has crumpled up to the back seats, highlighting the intense force the Prius experienced.

However, the deformation inside the rear passenger cabin was minimal, meaning severe injuries would have been unlikely.

Still, the importance of wearing a seat belt in the rear seat couldn't be clearer.

BAHOUTH: Your babies weren't in there, you're good.

Eh?

No, I know.

They were not in there.

I know.

They were not in there.

Oh, God, imagine if they were.

(gasps) BAHOUTH: I know.

LYNN: So I never thought I'd feel like this.

I thought it was just a game.

Do you know what I mean?

But it's, like, real.

Yeah.

Sort of...

It's not, but it, it, yeah.

Mm-hmm.

God, it's really got me.

Fla, flaming Nora.

Yeah.

♪ ♪ NARRATOR: The Prius is a hybrid car.

If damaged, the battery could catch fire, posing an additional risk to occupants and first responders.

♪ ♪ But in this case, the battery remained intact.

The car's crumple zones absorbed the impact as designed, protecting the battery.

As a result, there was no risk of a battery fire.

But can Andy and Marcus figure out the scenario that led to the Prius getting hit, using only the evidence left at the scene?

SHELTON: It's apparent that someone probably overreacted to the crash occurring in front of them, and then, possibly, an inattentive driver drove into the back of them.

So that's, that's kind of a, a clear and defined crash that's separate from everything else that we're looking at.

NARRATOR: Tito, an experienced U.S. driver who's based in the U.K., spots the danger early.

Remotely driving a Ford F-150 pickup, Tito reacts quickly, even though the flying grit has reduced visibility.

TITO: Oh, (bleep) hell, what the hell's that?

Oh, my goodness!

(tires skidding) (vehicles collide) What?!

NARRATOR: Tito may have benefited from the higher driving position of the truck.

TITO: Hey!

THOMAS: Taller vehicles can have some safety advantages, including the fact that you just have better visibility.

You're riding higher, you're able to see more.

They often are also larger and heavier.

And this has benefits in a crash because of just basic physics.

(vehicles collide) When you're coming against smaller vehicles, your vehicle is going to have a safety advantage.

♪ ♪ NARRATOR: For the crash forensic team, this analysis is straightforward.

That side of the, this section of road is higher than this side.

So these are locked tire marks, and they're tracking directly in a straight line, so the car did not yaw.

So the F-150 is coming in a straight line, and it's just followed this curved path, and it's just kind of come to a rest gently there.

♪ ♪ NARRATOR: But is this how Tito remembers the crash?

TITO: Wow.

Oh, my gosh, look at that.

BAHOUTH: Look at your car.

It's all right.

Did you mean to, to move over?

Yeah, I was just, like... Just holding on tight.

...holding on, 'cause I didn't want to hit anyone.

Okay.

TITO: Wow.

You could drive away, right?

Right.

It looks like it.

No.

Tire's intact.

Yeah.

So this is interesting, because it's a higher-framed car.

Yep.

Uh, a lot of trucks in the U.S.

Yes.

And, um, you know, we, we've got some interesting cargo... (chuckles) TITO: Yeah.

BAHOUTH: ...in the back.

TITO: I'm surprised it didn't go through.

BAHOUTH (chuckling): You know, you fared really good in this-- let's take a look inside.

TITO: How about the passenger?

Passenger's okay?

BAHOUTH: So, as a belted occupant in, in the passenger side here, the dummy was jostled around.

TITO: Okay.

BAHOUTH: Not a big deal.

He's belted.

In this impact, pretty good.

You walk away.

We're good to go.

TITO: Whew!

NARRATOR: Lynn and Tito managed to avoid hitting the truck since they both reacted quickly to the unfolding situation.

Natasha Merat is an experimental psychologist researching car safety.

For her, the footage is revealing.

As he's coming towards the crash, he tries to avoid the crash, like in the real world.

What the hell's that?

Oh, my goodness!

MERAT: Instead of just braking, he actually tries to move out of the way by steering, which is more of an experienced driver's behavior.

Whoa, whoa, whoa, whoa.

MERAT: With Lynn, she's well behind.

She sees it all happening way ahead.

She slows down even more.

She's sort of avoided the crash.

But as is also, again, typical in these situations, she ends up being rear-ended by another vehicle, which happens, again, in the real world.

NARRATOR: Being rear-ended is a reminder that for drivers like Lynn, danger on the road can be behind the driver... (tires skid) ...as much as in front.

You just got to be so careful of what's behind you and what's in front of you and what's at the side of you.

You can't just be centered on your own little world.

You've got to be aware of everything all around you.

Yeah.

When you're on the motorway, especially.

NARRATOR: Having shown Tito his F-150, Janet now wants to show him one of the other cars on the tarmac.

You had mentioned you have a Dodge minivan.

Yes, in... Yeah.

When I go visit the States, that's, that's what I drive.

Yeah, let's go take a look at it.

NARRATOR: The minivan was driven by Chenhui, one of James's team drivers.

During the crash, it experienced multiple collisions.

And from the wreck, it's clear a major safety device came into play.

Airbags.

The airbags used in today's cars originated in Japan in 1964.

DAVID TWOHIG: So a Japanese engineer called Kobori-san came up with the idea of using a chemical impellent to create a controlled explosion and generate a lot of gas in a very short time.

NARRATOR: Later, airbags were developed to inflate in around 30 milliseconds and were introduced into high-end vehicles in the 1970s.

Today, they're a standard safety feature in every new car.

But they have their limitations.

Airbags are designed to deploy once during a crash.

So, for subsequent events, they're not going to have their full effectiveness.

Automotive manufacturers would love to be able to design against multiple impacts for one vehicle.

It's difficult, though, because after a first impact, an occupant might be inside the airbag, so to speak.

NARRATOR: If the same airbag deploys a second time while an occupant is already cushioned against it, the controlled explosion could injure rather than protect.

The occupants of this minivan would have encountered this problem, since it experiences multiple impacts.

Its first point of contact is with the parked black Audi A6 towing the camper.

♪ ♪ It's at this point the front airbags inflate.

But then it slams into the parked blue Ford C-Max, cannoning the C-Max into the tractor trailer's cabin.

Here, the minivan's side airbags deploy.

♪ ♪ It then smashes into the tractor cabin itself and finally collides sideways with the truck's trailer.

♪ ♪ The front and side airbags deploy during the first two impacts.

However, since they are designed to deflate quickly to avoid trapping or suffocating injured occupants, they offer less protection during the final side-on collision.

TITO: Oh, my goodness, man.

BAHOUTH: Yeah.

Yeah.

This car went through a lot.

(chuckles) Uh, it wasn't just one impact, obviously, because the entire front is destroyed, the side is destroyed.

You can see toward the back, we've got rear impact.

We had a dummy sitting in the front passenger seat.

TITO: Yeah.

BAHOUTH: So the airbags deployed.

But at the end of the day, it didn't do a whole lot.

Okay, no.

Airbag or not, with this much intrusion, with this much damage to the occupant space... ...nobody would have survived that.

No.

(tires skidding) TITO: My goodness.

It's just shocking that within mi... Just seconds, really, seconds... ...a solid thing turns into a crushed piece of metal.

BAHOUTH: Yep.

This is the car seat with the seat belt that held the car seat in.

Oh, my God.

Yeah.

So, if there were, if there were a child sitting back there, they didn't make it.

No.

100%.

That is a huge impact.

TITO: I will continue being a defensive driver.

BAHOUTH: Good.

Major impacts like this, just... Any car, any car will get crushed.

NARRATOR: But can Marcus pick apart the clues in the crushed metal?

ROWE: I think the white vehicle, the people carrier, has probably-- to be confirmed with paint transfers and other things-- had an impact with the blue towing vehicle.

It's put it into a sideways yaw, which has then resulted in a sideways, fairly significant kind of slapping impact.

And it's gone quite high, actually, after impact, onto the lorry.

♪ ♪ NARRATOR: Marcus is correct about the circumstance that led up to the Dodge's crash.

He has incorrectly assumed the blue Ford C-Max was driving rather than parked on the shoulder.

But he has figured out which car struck the truck first.

♪ ♪ The C-Max cannot have got to its resultant position if the white vehicle was here.

So the C-Max event must have happened before the white vehicle event.

♪ ♪ The blue Ford is first into the collision, followed by the white people carrier, followed by the F-150.

That's what the evidence is, uh, is telling me at this point.

NARRATOR: And Andy has found some physical evidence that confirms this theory.

The Dodge came into the side of the Audi.

In the process, this blue paint-- which, my initial assessment was, it was from the side of the truck... Mm-hmm.

It's actually from the Ford.

BAHOUTH: Cool.

SHELTON: So, the front end loaded up into the back of the Ford.

You got the... Yeah, that...

The white bumper was actually deposited in... Nice.

...here.

Wow, that's so neat.

And we removed that out of there in the process of, of assessing it.

And then I told you, it brought some of the Audi with it.

Yeah.

This was trapped in here.

It's a black panel with the green panel adhesive on the back of it.

Wow, so that...

So it, it brought part of the Audi to the Ford and left it behind.

NARRATOR: Across the track, Marcus has spotted something interesting with regards to the Porsche Boxter, driven by Caitlan, the youngest and least experienced driver.

♪ ♪ So, if you kind of stand quite close to me and look down the line here, you can hopefully see these two fairly clear tire marks.

So they start in this lane, and then they come into this kind of area next to this barrier.

You can see the black marks of the driver's side tires coming up onto the barrier, and they come increasingly up until the sidewall of the tire actually makes a really significant mark on the lower edge of the barrier.

And at about the same time, there's contact on the barrier with the wing mirror.

♪ ♪ NARRATOR: Marcus has perfectly described the contact Caitlan's Porsche made with the barrier without having seen it happen.

CAITLAN: Um...

I can't see!

(loudly): What is going on?!

(tires skidding, vehicles colliding) I've just crashed.

ROWE: So, we've got the route of the Boxster really well nailed down.

And we also know the driving behavior of the Boxster.

We don't know the speed at this point, but we do know there's really good early observations.

There's avoiding action and there's heavy braking.

So we can say, you know, "That driver is awake, they're on it."

You know, they, they've taken avoidant action.

Sure, they've ended up making contact, but at quite an early stage and quite a good distance back, they have reacted to the impending danger ahead of them.

(loudly): What is going on?!

NARRATOR: Caitlan comes to a stop about 25 feet from the tractor trailer.

But then, she accelerates directly into the back of it.

Why?

Oh, my God.

(laughs) Wow.

Not so beautiful car anymore, huh?

Yes, what a shame, but what the hell?

I don't know how, how I managed that.

Mm-hmm.

I don't know how I've ended up under there.

That is, that is bad-- that is really bad.

CAITLAN: Wow.

BAHOUTH: Describe what you remember, though, as you came down.

So, what I vaguely remember is just a big cloud of smoke.

I don't recall seeing that.

I didn't see the lorry at all.

BAHOUTH: Okay.

CAITLAN: But I remember I did put me foot on the brake, and I did accelerate a little bit to get out of the smoke.

(tires skidding) NARRATOR: The video evidence suggests that Caitlan may have reacted to the sporty Mercedes ML, driven by team driver Aisha, speeding past her as she remained in the right-hand lane.

In the U.K., this is the fast lane, and a dangerous place to be stationary.

MERAT: Caitlan does just stop.

She's obviously in shock, the smoke is coming in, she's really not sure what she, um, should do.

And then she is actually still seeing that she should move out of the way and get herself out of that situation.

CAITLAN: It all happened so fast.

BAHOUTH: Yeah.

It was, like, just a big blur, but honestly, I'm, I'm gobsmacked.

I'm gobsmacked.

Yeah.

BAHOUTH: So, you ended up not having enough momentum, enough velocity to actually go under.

Yeah.

(chuckles): Which is probably very good.

Yeah.

So, would I have been safe, or...

I think you'd be okay.

Wow.

Obviously shaken, maybe some bruises from the seat belt, but you would have walked away okay.

Wow.

Yeah.

NARRATOR: Caitlan would have survived the crash due to one of the simplest of safety features: the humble seat belt.

The three-point seat belt has saved more lives than any other car safety device.

First invented in 1951 by Americans Roger W. Griswold and Hugh DeHaven, the modern side-buckled version was created by Swedish engineer Nils Bohlin and Volvo in 1959.

♪ ♪ TWOHIG: Rather than trying to make money out of this invention, Bohlin and Volvo actually gave the technology to the rest of the world.

So not only did Nils Bohlin save millions of lives, he never sought to make a penny out of his invention.

THOMAS: The point is to spread the crash forces over the strong parts of the body, like the chest and the pelvis.

Modern-day seat belts have advanced technologies, like pre-tensioning and load-limiting.

What these features do is, they help to remove the slack out of the seat belt system.

At the end of the day, the best thing that you can do is put your seat belt on.

The seat belt is still the most effective way to reduce your risk of injury in a crash.

BAHOUTH: You did pretty well.

I'm fairly surprised that I would've been okay, because there's no roof or nothing on it.

Mm-hmm.

So in my mind, I was sort of thinking I might have flew out, or something like that.

Yeah.

If you were unbelted... Then yeah, definitely.

...that's a distinct possibility, for sure.

BAHOUTH: If you're belted... CAITLAN: I'm safe.

BAHOUTH: ...you're literally unbelting yourself and you're walking away.

CAITLAN: Wow.

BAHOUTH: You did great in this car, for sure.

Well, don't underestimate us young drivers.

(both laugh) ♪ ♪ NARRATOR: The Volkswagen Golf, driven by adrenaline junkie Luke, has come to a stop about 40 feet on the far side of the tractor truck.

ROWE: These are the track marks of the Golf, and the left-hand side is here-- as you can see, that's underneath the lorry.

So we know that the Golf has come through before the lorry is across the road, if that makes sense.

SHELTON: The Volkswagen appears to have had to have traveled through the location of the trailer from the delivery truck.

So in order to travel through it, we know the truck wasn't there.

NARRATOR: Marcus and Andy know that the Golf could not have passed through the truck.

They can also tell that the Golf didn't squeeze past the cab of the truck before it blocked the road.

If that had happened, any damage to the Golf would be on the other side.

So can they figure out what really happened?

Oh, oh, oh!

Jesus!

BAHOUTH: So, you can see... LUKE: See, it looks unscathed here, doesn't it?

Yep, absolutely.

So literally, the impact was the side... Yeah.

...right into it there.

BAHOUTH: Started here.

LUKE: Oh, wow, yeah.

BAHOUTH: You can even see the white paint.

LUKE (gasps): Look at that.

BAHOUTH: Yeah.

Tore through it-- that's gotta be part of the metal.

LUKE: Oh, my God.

NARRATOR: Back at the truck, the investigators make a breakthrough that could explain the damage to the Golf.

So we've been looking constantly now for a solution that allows the Golf to get through to where it is, and we found the secret.

SHELTON: There's a contact from the lower corner of the trailer that's actually gouged into the roadway that's indicated that the trailer has actually come up in this kind of configuration.

NARRATOR: The front right corner of the second trailer has clearly made contact with the ground.

For this to have happened, something must have struck the back left side of the trailer, forcing it up into the air.

The impact of the Porsche wasn't significant enough to have caused the trailer to tip.

However, damage to the luxury sedan Audi A8, driven by team driver Mark, which is now a crumpled wreck 20 feet from the truck, suggests it might be the reason the trailer tipped.

So, if it's come up from there, created a new hypothesis: is it possible the Volkswagen actually could have gotten under the, a portion of or all of the trailer at some point?

NARRATOR: The investigators' theory is that the Golf didn't go through the truck, but under it.

The truck trailer is pushed onto two wheels as the Audi strikes it... ♪ ♪ ...gouging out a piece of the roadway as it lurches, creating a gap underneath, which the Golf drives right through.

♪ ♪ But is there any evidence available to the investigators to give them confidence in their theory?

SHELTON: What we identified is red paint on the bottom of this surface.

It's the only red transfer we found on the vehicle.

NARRATOR: The traces of red paint prove the Golf contacted the underside of the trailer.

The trailer actually has to have been up at some elevation for the Volkswagen to get underneath it.

The only thing we can think that could have caused that kind of opening is the impact of the Audi striking the trailer first, the Volkswagen shooting underneath the edge of the trailer as it went by, then the Porsche coming in behind that.

♪ ♪ NARRATOR: Using the lidar scans to remove the smoke from the crash scene, it's possible to visualize how the Golf squeezes under the trailer at the very moment the Audi forces it onto two wheels, leaving gouge marks on the tarmac.

A one-in-a-million set of circumstances that could have saved the driver's life.

♪ ♪ This scenario explains the extensive damage to the Audi.

SHELTON: The primary direction of force is directly through, uh, the, basically the tip of the steering wheel.

Mm-hmm.

Which is kind of the worst place for a driver to be.

I, I wouldn't expect to see very good condition on this one.

Yeah, yeah.

BAHOUTH: We've got so much intrusion.

His legs are crushed.

It's probably not survivable.

NARRATOR: It also explains the much lighter damage to the Mercedes ML driven by team member Aisha.

SHELTON: As the truck's coming back down, the black Mercedes catches the corner of the door that's swinging.

It flattened the left front wheel, which has left a low tire scuff all the way to the final rest location of the Mercedes.

We've got A.B.S.

brake indication actually once we get into the grass, but no evidence of braking out in this area on the part of the Mercedes.

NARRATOR: And what about the passengers in the Mercedes?

Before the crash, Janet installed two crash-test dummies.

One was belted, and one was deliberately left unbelted.

(tires skidding) The car caught a glancing blow off the rear door of the truck.

Both the belted and unbelted passengers would have been shaken but unharmed.

This time.

♪ ♪ But what about the occupants of the Golf?

Would they also have been unharmed?

ROWE: The Golf has gone underneath the trailer.

There's been some contact between the underside of the trailer and the Golf on the A-pillar that you can evidence together the cause and effect of those two areas.

NARRATOR: While the driver's airbag was deactivated to accommodate the robotics, the passenger's airbag could have deployed, but didn't.

And Janet has a theory as to why.

The impact came so high on the car, the airbag sensors are down... Yeah.

...on the bumper area.

It may have missed it.

Yeah, yeah, yeah.

The, the sensors might not have picked it up.

LUKE: Yeah, yeah.

NARRATOR: The team won't be able to confirm this theory until the Golf is returned to Cranfield University, and the airbag data is analyzed.

(tires skidding) The damage to the Golf may appear minimal, but the dummy inside tells a different story.

Before the experiment, Janet applied colored greasepaint to the mannequin's head.

♪ ♪ Paint traces left on the car reveal where the dummy struck hard surfaces during the crash, providing clues about the injuries this passenger would have received.

BAHOUTH: Let me show you something.

That is so close, isn't it?

Well, it's...

It's not just so close-- he hit it.

He actually struck the car.

Oh, wow.

Look, the red paint.

You can see it, oh, yeah?

That is insane, isn't it?

Yeah.

NARRATOR: The black box data, once fed into a crash simulator, confirms what the greasepaint is already revealing.

And the results are sobering.

♪ ♪ The brief but substantial contact with the trailer causes the forward pillar to buckle, striking the passenger on the head.

How, um, injured was the person in it, then?

That's going to be a severe head trauma, there's no doubt.

NARRATOR: The Golf's pillar may have buckled only a few inches, but if that force had been transferred to the passenger's head, the injury could have been fatal.

(engine revving) (tires skidding) LUKE: And obviously, what are the injuries I sustained?

BAHOUTH: For you, maybe some head trauma.

No.

Yeah.

Really puts it into perspective, doesn't it?

You don't know what's going to happen and the injuries that you sustain, so, yeah, it's just... Don't know what to say, really.

We're happy you weren't actually in there.

Yeah, no, of course.

♪ ♪ (alarm blaring) He's veering, he's veering.

MERAT: You can watch Luke's pupils.

They are dilating.

Oh, oh, oh!

He's definitely got all of the responses of a shocked and immersed person.

He's absolutely in that environment, and he's trying to avoid it, and he just can't believe it.

Whoa!

NARRATOR: For Natasha, it's proof of the validity of the experiment.

Although the drivers were in remote control pods, they still experienced this crash.

I've never really been in something this serious before.

At this speed and when something happens this quickly, you have no time to react.

It really is quite a scary situation to be in.

I probably will drive a bit more differently.

Be more cautious, as well-- cautious of other people, especially on the motorway.

♪ ♪ NARRATOR: According to crash analysis expert Janet Bahouth, of the volunteer drivers, only Luke would have faced the possibility of serious injury.

Tito, Caitlan, and Lynn more than likely would have been able to walk away.

(tires skidding) Although that's not the case for drivers from James's team.

While Pete in the white van and Aisha in the Mercedes would have survived... ♪ ♪ ...if Chenhui had actually been in the Dodge and Mark in the Audi, their impacts would have likely been fatal.

As for the cars parked on the shoulder... ♪ ♪ ....those in the towing vehicle took a heavy hit, but would most likely have survived.

However, anyone still in the Ford C-Max may well have lost their lives, confirming that the safest option is to exit a parked car on the shoulder to avoid any potential collisions.

♪ ♪ Having laid out their theory, Marcus and Andy now get to watch the crash unfold for the first time, to see if their findings are correct.

BAHOUTH: Here we go SHELTON: It's exciting.

(tires skidding) SHELTON: Some cars were slower, some cars were faster.

BAHOUTH: Mm-hmm.

SHELTON: Truck comes over-- wow.

Did you see it?

The trailer come up?

ROWE: Yeah.

Yeah, yeah, yeah.

Hey, look at the Porsche.

She stops and then drove inside of it.

BAHOUTH: She pulled over knowing something bad was happening, and then realized, "I'm in all this smoke.

I don't like this smoke-- get out."

And that's why she continued...

So she was trying to drive through a thick smokescreen.

BAHOUTH: She didn't know... ROWE: Oh, right.

BAHOUTH: She didn't know the tractor trailer was there.

♪ ♪ SHELTON: The blue car that really didn't make any sense how it had interacted was stationary.

Was stationary.

Yeah, yeah, but that...

Absolutely.

We always had a question mark... Had a question about... ...over the physics of that, so that's...

The physics of the rotation on it.

Yeah.

So, that answers a lot of questions.

♪ ♪ NARRATOR: The stationary blue C-Max aside, Andy and Marcus very accurately deduced the individual elements of this complex incident, proving the value of their methods and experience.

♪ ♪ SHELTON: Coming out here, of course, I didn't know what to expect.

Got here, and it was a heck of a crash.

Big mess spread out over an immense distance.

We worked all the way through it.

We'd come to a relatively solid hypothesis.

I was, like, the kid with the answers to the tests.

SHELTON: Right.

And I watched you guys, and I, I saw what you were doing and how you were looking at everything.

The magic happened when you picked up the corner of the back trailer.

It broke open the whole case for you guys.

Yeah.

Right.

It was fantastic to see that, I was so excited.

There was no way the Volkswagen could have gone through the truck.

(chuckling): Right.

It had to go under the truck.

Yeah.

(tires skidding) SHELTON: Having the ability to go back in at the tail end and watch the video, what transpired, to see what I ascertained in the field and how it compared to what actually occurred was really mind-boggling in this case, because it was-- we were so close to, to what had actually transpired without ever looking at any data.

We're able to show that what we do in the field helps us to find the truth so that we can speak the truth and defend it later.

And it was a, it was a great process to be able to do that.

I was... Just fantastic.

Wouldn't you like to have this on every crash?

(Bahouth chuckles) ROWE: Seeing that Golf under the lorry, it's unique, but we read it correctly.

The science doesn't lie.

It's not luck.

It is a scientific art form to read and diagnose collision scenes.

And we've done it right.

♪ ♪ NARRATOR: But what of the rest of the experiment?

What has this high-speed pileup revealed about the vehicles themselves?

BRIGHTON: All the vehicles are interesting in themselves, not only because of the vehicle, but because we've got the data, we've got the footage, and we know exactly what happened to them.

What's the first thing you notice here?

MAN: The driver's seat is not where it should have been.

BRIGHTON: Exactly.

We brought all of the vehicles back to the university, and we're now starting to use them to teach the next generation of automotive and motorsport engineers.

We hear consumers complain all the time that, like, A-pillars and B-pillars are getting bigger and bigger.

Yeah.

And visibility's getting worse.

But...

But clearly...

If that had been smaller... ♪ ♪ (exhales) It's interesting that the airbags haven't gone off on the passenger sides.

MAN 2: Yeah.

NARRATOR: James and his team have now analyzed the black box data from the Golf and uncovered a possible reason why Luke's passenger airbag didn't deploy-- a set of circumstances that ultimately would have led to serious injury or even death.

The deceleration rate was much less than five G. The deceleration was simply too low to trigger the airbags, so they simply didn't deploy.

♪ ♪ NARRATOR: The Dodge highlighted a drawback common to many vehicles when it slammed side-on into the tractor trailer.

It's far more significant to have a side-on high-energy impact than it is to have a front-on high-energy impact.

NARRATOR: Front and rear crumple zones save lives.

But these are harder to build into the sides of cars.

But what really stands out is that while cars can be engineered to be safer and safer, there is still a weak link in the chain.

You cannot 100% protect the driver from every scenario.

And so the driver has to be vigilant of what they're doing at all times.

There is an interaction between humans and systems.

So yes, our cars are getting safer, but the roads are much more complex, vehicles are much more complex, people are still speeding.

And obviously, the faster you go, the more likely you are to be involved in a crash.

♪ ♪ NARRATOR: The human element brings with it poor driving and speeding, leading to severe and potentially fatal accidents.

Oh!

Oh!

NARRATOR: But is there a solution?

For true safety, perhaps the ultimate answer will eventually be to remove the driver from the equation completely.

BRIGHTON: The future of vehicles is really going to be autonomous systems embedded into cars so that they have a better awareness of their surroundings than the human within them.

But nonetheless, you are still within a road environment where lots of things can happen.

And protecting yourself from those risks is really paramount for road safety.

NARRATOR: Until autonomous vehicles become the norm, the fight goes on.

Engineers will continue to design around humans to build safer and safer cars to cope with the random, complex nature of real roads and real drivers.

♪ ♪ BRIGHTON: Bringing the human element in and getting their reaction really does help us to understand how the cars and the human as a combined unit behave in this situation.

♪ ♪ NARRATOR: After experiencing the crash and examining the damage done to their cars, the volunteer drivers are eager to see how the experiment really unfolded, and how it compares to their recall of the event.

I did not see that lorry at all.

No, no.

Even though it's bright blue, it's massive, I didn't see it.

LUKE: I know!

NARRATOR: This is the first time they have seen the entirety of the crash.

The dashcam and drone footage reveals just what they went through in crystal-clear detail.

CAITLAN: Here we go.

Happened so quick.

(tires skidding) TITO: Boom, boom.

Look at the white Dodge.

TITO: Oh, my goodness!

(Lynn moans) LUKE: Literally clips the caravan first, then spins.

Look at, look at Luke.

Whoa.

Look at you there, Luke.

LUKE: Yeah, look at the trailer as it comes up.

LYNN: Oh, for...

So I hit, like, the underside, almost.

Aye, you're right, you went through that little bit there, didn't you?

TITO: Wow!

BAHOUTH: There's red paint underneath.

(Caitlan groans) LUKE: That is, like, lucky timing, I'd say.

Yeah, it was.

And that's me skidding.

LYNN: That's Tito coming up.

TITO: That's me on the brakes.

BAHOUTH: Watch the Mercedes come in.

LYNN: Whoa!

LUKE: Oh, my God!

Then there's me.

LUKE: Just, you stop and then you just slowly go, "Oh, I'm just gonna go into the trailer."

CAITLAN: It was, like, brain fog, I think.

LYNN: So were you just panicking?

CAITLAN: Yeah... LUKE: And you thought, "Oh, yeah, he's going off, so I'm going to go off, as well."

LYNN: So you tried to follow him, then, haven't you?

CAITLAN: Yeah.

LYNN: Yeah.

And I'm all the way up here!

(tires skidding, vehicles collide) Oh...

But as long as I survived and me passengers did, that's the main thing.

Well, we're all alive... Yeah.

That's the main thing.

...and we're all here to tell the tale.

Well, take what you learned from here.

Um, you'll, you'll remember it.

LYNN: Gonna remember it the rest of me life.

LUKE: 100%.

LYNN: Yeah.

BAHOUTH: Yeah.

LYNN: Yeah.

You're a great crowd, and, and as a memento, don't forget... LYNN: Oh, look at that!

(Lynn and Caitlan exclaiming) Take your license plates.

LUKE: Thank you.

Absolutely.

Yeah, hey, thank you very much.

CAITLAN: Thank you.

LYNN: Fridge magnet.

All right, nice to meet you.

Safe driving.

Let's go.

Whoo!

♪ ♪ (all cheering) I am mind-blown and I am gobsmacked about it.

It's such a scary situation, and obviously, stuff like this happens on a daily basis.

It does just take that one car to cause chaos.

LUKE: It goes to show it doesn't matter how good you are as a driver.

You could be the best driver in the world and have so many plans or exit routes, but there's only so much you can do, like, planning you can do.

There could be other people around you, especially on the motorway.

You have no control in that situation.

LYNN: I am really careful, maybe sometimes too careful.

But it doesn't matter how careful you are, you can still be in a really serious crash.

TITO: It's definitely going to stay with me.

It's definitely impacted me in how I, how I drive in the future.

Creating a unique experiment like this opens a window to what we might be missing with those lab tests.

And how can we now look at improving the future design of vehicles so that we all drive around in a much safer manner?

BAHOUTH: I hope that people watching this program will get a lot out of it, to change behavior, to slow down, to wear seat belts, to not be distracted.

And hopefully, the message for safety really just outshines everything.

♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪ ♪