Original subtitles

(roadway noise)

If you crash your car,

are you better off in

a small modern Five Star Safety Rated car

or in something big and solid?

(roadway noise)

The only sensible way to resolve this

is to smash this one into this one

and see what happens.

(intense orchestral music)

(cymbals crashing)

(electronic whizzing)

I've always been fascinated with how the world works,

and I've got lots of questions about why things happen.

To find out the answers,

I'm gonna blow stuff up.

(electronic whizzing)

(car tires screeching)

(cars banging)

New Zealand's first recorded car crash was

in 1904 when a car traveling on Hobson Street collided

with a train car.

Since that day, car collisions have become

an everyday occurrence.

In order to understand more about cars and collisions,

they're regularly crashed in controlled circumstances.

(glass breaking)

(car crashing) In this episode,

we're going to crash a large, heavy, old car into

a small modern car to find out which one you

and your family would be better off in.

(metal clanking)

No one's ever done this test before

because when ANCAP do it they compare vehicles within

the same category.

So this is the first time ever, in New Zealand,

that anyone's taken

a modern small Five Star Safety Rated car

and smashed that into a much bigger, older car.

Even the experts don't know what's gonna happen.

So let's start off with getting our heads around

the basics of smashing stuff into stuff.

(cars tap)

The first and most important thing to understand is

that you can't create or destroy energy,

you can only transform it into different kinds of energy.

Now all moving objects have kinetic energy,

and when they collide with something (cars tap)

all of that kinetic energy has

to go somewhere almost instantaneously.

So what happens to it?

Sir Isaac Newton made this little contraption,

and it isn't just a quirky desk toy,

it actually demonstrates one of the fundamental laws

of the physical universe.

The law of conservation of momentum says

that in a collision,

energy isn't lost, it's transformed.

So this is an elastic collision,

and when the balls collide, the energy is transferred back

and forth, but there's a second type of collision

where something quite different happens.

(intense music)

(muffled bang)

In an inelastic collision,

the two objects effectively remain stuck together.

Now in the real world, there's no such thing

as a perfect elastic or inelastic collision,

it's always a mixture of the two and some

of the energy's also lost in the form of heat and sound.

(car crunching)

But the important thing to understand is that all

of that kinetic energy has to go somewhere,

and in the case of a car crash,

it goes into destroying the vehicles,

but just as importantly,

some of it also goes into destroying us.

To put all this theory to the test,

I've come to a top secret high tech testing facility

in Christchurch.

Holmes Solutions are experts

in full scale dynamic impact testing

which means they can wreck just about anything,

and this is their crash test footage.

I've come up with a cunning and fun way to illustrate

the science of collisions.

We've got two supermarket trolleys,

and because supermarket trolleys never go in

a straight line, we've got a wire rope

which will guide them in together.

And then we're going to basically smash them together

at different speeds and at different weights to see

what impact that has on the collision.

And three, two, one. (intense drum music)

(trolleys clanking)

Mass and speed determine the amount of force in a collision.

(bright string music)

Both trolleys are the same mass

and are traveling at similar speeds,

so the energy of the collision is distributed evenly between

the two.

But what if my trolley weighed a lot more?

What if this time it had more mass?

We're going to add 130 kg to the trolley on the right.

(trolleys clanking)

Not the most controlled experiment,

but just pretend for a moment the trolley on the right

is the older heavy car and the one on the left

is the new modern safe car.

(bright resonating music)

As you probably already suspected,

mass matters.

Apply this to our car crash,

and our little car is in big trouble.

That time I won the collision because my car was

the bigger, heavier one so it pushed

the smaller, lighter one out of the way.

But what would happen if we took this experiment

to ridiculous extremes?

(intense music)

Yup that's a 2,300 kg concrete block,

and this is something I've always wanted to do.

Ever had a supermarket trolley hit your car?

Time for a little revenge.

Now I know what you're thinking,

all that theories all very well,

but what would it look like if a supermarket trolley was hit

with the amount of energy equivalent to slamming into

a concrete wall at 90 km per hour?

Watch this.

(bright orchestral music)

Speed times mass equals big travel for our little trolley.

Three, two, one.

The force from the concrete block has to go somewhere.

Remember we said energy can't be destroyed only transformed.

Here we see the energy transformed into a force

of destruction.

Since the concrete block doesn't break or give at all,

the full force of its weight goes into the trolley.

(intense resonating music)

The big takeaway here is that our older, heavier car

is going to have a huge advantage in a collision

with a smaller, modern car.

It's pretty clear that when it comes

to collisions, weight matters,

but we're only just getting started because our little car

has got some really big ideas behind it.

The 2013 Toyota Yaris has been described

as a willing little unit,

smooth, quiet and having plenty

of punch for its size.

More importantly for us,

it received a Five Star ANCAP Safety Rating.

(glass breaking)

Eighteen years earlier in 1995,

the Holden Berlina was praised for its power

and reliability.

It never received an ANCAP Safety Rating,

but some models were fitted with one

of those newfangled airbags on the driver's side.

The problem with collisions is

that they car stops almost instantly,

but the passengers don't.

So clever people came up with this idea.

(airbag bangs)

So how the airbag works is that instead

of a sudden jarring collision with the metal,

the passenger hits the airbag which absorbs the energy

and provides a softer landing.

(deep resonating sound)

So what other clever ideas have scientists come up

with to protect passengers?

(resonating electronic music)

The Berlina and Yaris both have airbags

the difference being the Yaris has seven while

the Berlina has one, well, had one.

We just used it in our little airbag demonstration.

Pre-tensioned safety belts are another feature

the Berlina lacks.

The Yaris has a reinforced passenger compartment

and crumple zones, a structural feature designed

to absorb energy in a collision rather than passing it on

to its passengers.

When it comes to surviving crashes,

there are two magic words, crumple zones.

How they effectively work is they absorb the energy from

the collision, and they slow the deceleration.

So I'm gonna build one myself from egg cartons

and see what the impact is on crash test Nigel.

Three, two, one.

(trolleys crashing)

(laughing)

After that demonstration of why you should always wear

a safety belt, one was provided.

All right, three, two, one.

Now the important thing to consider here is

that the trolleys are traveling at similar speeds, right?

But unlike before, when the heavier trolley bulldozed

the lighter trolley backwards,

our egg cartons have deformed and crumpled to absorb some

of the impact of the collision,

and it's no where near as pronounced as before.

So this is a perfect example of how crumple zones work

because all of that kinetic energy from

the collision has been absorbed,

egg cartons have all deformed,

but it means a slower deceleration

and our passenger, crash test Nigel, is much better off.

But can crumple zones save you from a catastrophic injury?

Later, we pit science against brawn in a fight

to the finish.

(electronic whizzing)

(intense music)

(car crunching)

There are three stages in any collision.

There's the first stage, the initial impact.

The second stage when the outside

of your body first contacts the car,

and the third stage when things like your brain impact

on your skull.

(intense music)

To show you what that's like,

I've almost exactly recreated the human skull here

with my Perspex bowl and inside of that, a jelly brain.

Then we're gonna crash the two trolleys together,

and we'll see what happens when soft things hit hard things.

(banging)

Think of the brain as an egg yolk inside an eggshell.

The eggshell is the skull.

(resonating music)

In an accident, the brain's injured by the pulling

or tearing of delicate brain tissue

which is the consistency of poorly set jelly leaving

it bruised or damaged.

That was a pretty catastrophic brain injury,

as evidenced by this rather large tear to the temporal area

of the brain.

So now what I'm gonna do is I'm gonna swap this one out

for a fresh one, we'll put a crumple zone on the front,

and then we'll see what happens.

(resonating music)

(drill whirring)

(trolleys crashing)

Usually the damage is caused by the sudden acceleration

and deceleration of the brain.

One of the most important reasons for absorbing energy

in collisions, without passing it on to the occupants,

is to protect the brain.

So the science has worked exactly as it should.

That crumple zone has absorbed all of that kinetic energy

which meant that our brain decelerated a whole lot slower,

so it's actually in pretty good shape.

(intense music)

(trolleys crashing)

If you take speed out of the equation,

big will defeat small.

But car collisions aren't quite as simple as that.

Modern safety features play an important role

in absorbing impact and protecting occupants.

At this point, I really don't know

which car I'd rather be in.

The good news is now we get to find out for real.

It's time to bring in the crane, wire up the cars

and get on with crashing big car into little car.

You might've thought we'd be using the old tried

and true method of a brick on the accelerator

to propel our cars, I certainly did, but we're not.

While our cars have to be driverless,

they still need to be controllable in terms

of speed and direction.

So our cars will be powered by gravity.

The key to it all is this crane and that concrete block.

The cars and crane are connected through a system

of pulleys and wire.

After a few careful calculations,

the five ton block will be lifted to a height of 25 meters

which will propel both our cars to a collision speed

of 70 km per hour.

Now it's time for a test fire of our mechanism.

So what's gonna happen is the crane will drop

a concrete block and that will instantly propel me

with a force equivalent to two Gs that way.

I'm gonna have the engine running,

so I've got power steering and brakes.

Three, two, one.

(wires scraping)

Oh shit.

Yeah, so I misunderstood.

(laughs)

I thought the crane driver was out and you were saying

to him, "We're gonna go on three, two, one."

And then it went bang, oh bang.

(car bangs and screeches)

I foolishly hit the brakes, so we need to go again.

(laughs)

It was the kickback.

You look like you. Yeah, yeah, yeah,

yeah, yeah.

From where I was standing I could see your eyeball

was dilated.

Yeah, yeah that was pretty good.

It was good.

Two Gs no problem just don't brake before

it's finished dropping.

That's the secret to this test.

(intense music)

(cables screeching)

So that went a lot better

because I didn't start braking halfway down,

but when that block drops,

you totally feel, instantly, two Gs of acceleration,

boom, straight down that track.

(intense resonating music)

The key to all of this is that the cars actually collide.

It almost never happens,

but the last thing we want

is two unmanned, uncontrolled cars careening off

in opposite directions at 70 km per hour.

Like the ones we used on our trolleys,

these wires will ensure that our cars collide,

so they have to be tested and retested.

Camera placement is crucial.

We only get one go at this.

We'll be employing 14 cameras, at different angles,

shooting at frame rates ranging from 25

to 5,000 frames per second

to ensure we capture every moment of this collision.

Those nifty little black

and white stickers might not look like much,

but they're tracking markers,

and they'll play a vital role in helping us record

what actually happens in our collision.

Real crash test dummies costs upwards of $400,000,

so we've had to improvise somewhat.

So there were two options for this part of the test.

One was I sit in the car, but that's just stupidity,

so instead, we've gone

for slightly weird creepy virtual Nigel.

(ominous music)

With their cars positioned and ready,

Dr. Chris Allington, Holmes Solutions crash test expert,

completes final checks on the crane and its load.

Remember, once that concrete block is lifted,

the entire crash area becomes live and any margin

for error is gone.

Okay guys, so we've got our crane all set up now.

We're about to start lifting the blocks.

This is when it becomes very real,

so safety first.

We'll have to make sure

the cameras are all turned on, armed,

ready, set up before we lift those blocks.

So anything that you've gotta do before those go up.

Then we'll start lifting our blocks up in the air.

When they get to the right height,

you'll hear over the walkie talkies, "Three, two, one go,"

and those blocks will come down.

Critical thing for everyone,

as soon as those blocks are an inch off the ground,

the whole system's live.

There's no point of return from there.

We have to make sure that everyone's well clear

of those cables.

The moment of truth is fast approaching.

If anything goes wrong from here,

that spells disaster.

(cables whizzing)

(block crashing)

(electronic whizzing)

(car crashing)

Finally, it's time for the real deal collision time.

We're about to crash a 2013 into a 1995 Berlina.

Science tells us that mass really matters in a collision.

(intense music)

The Berlina, weighing one and a half times the times

the weight of the Yaris, has a huge advantage in terms

of mass, but will this be counted

with the modern safety science onboard the Yaris?

Will airbags, crumple zones

and a strong occupant compartment combine to defeat

the heft of the Berlina.

I really have no idea.

Which would you rather be in?

Which car is going to win?

So here's how it works.

Our crane drops five tons of concrete 25 meters,

that pulls our cables tight, cars come hurtling down here,

hit the blue blocks, steering mechanism goes away,

towing mechanism goes away,

freewheeling all the way across here

and at something like 70 km per hour,

in about a couple of milliseconds,

all of that crash science comes together in

a quite spectacular way.

(intense piano music)

We're close now.

Almost live.

We've thought of everything or have we?

When that block goes up, it's too late.

This is the bit where it gets really serious.

Any number of things could fail.

A wire could snap.

A pulley could fail.

I see what you mean about tension at this point.

Like it's pretty tense. (laughs)

Yeah.

There it goes.

The block's going up.

That means we're live.

Crash time is moments away.

(muffled voice on walkie talkie)

Three, two, one.

(cables whirring)

(block crashes)

(cars crash)

(laughing)

That made me jump, yeah.

(laughing)

(intense music)

(cars crashing)

(cars crashing)

(glass breaking)

(metal crunching)

In real time, the violence of the impact was startling,

but over in a moment.

The collision was so instantaneous it felt like

it had two stages, before and after.

But in super slow motion, we get to see

what really happened.

(intense music)

The first thing that struck me was that what seems

so brief in real time,

is actually an incredibly concentrated sustained wave

of destructive violence.

We literally get to see energy transformed from one state

to another.

To me, it looks like the Berlina ate the Yaris

and spat it out.

Let's find out how it tasted.

But, look at this.

Still open the door.

That's amazing.

My god!

The first thing to consider here is

that the occupant area of the Yaris is still intact.

You can see the shock wave traveling through the Berlina

and its occupant zone, but not in the Yaris.

The airbags in the Yaris deployed successfully.

Obviously our crash test dummy wasn't up to much,

but the benefits of airbags to the occupants in

a collision are obvious.

First passenger compartment is basically untouched.

Like that's amazing.

Perhaps I should've attached some egg cartons to the Berlina

because the crumple zones on

the Yaris exceeded my expectations.

The Berlina is almost 50 percent heavier than the Yaris,

so the Yaris had to absorb a lot more

of the impact without passing it on to its occupants.

It's such a small car.

You would think that thing hitting it,

it would just destroy it.

Yeah, it's exactly like we saw

with the supermarket trolleys.

That crumple zones absorbs all that impact

and this is all that air space we had before

is all squashed up and crumpled up.

The severity of the punishment dealt

to the Berlina surprised me.

See straight away...

Yeah.

So that's just pushed all of this.

The interior of the Berlina really tells the story.

Will though big and tough, the Berlina's got a glass jaw.

(cars crashing)

Like all bullies, it can give, but it can't take.

It's lack of safety science means that its occupants have

to absorb more of the impact of the crash in their bodies

than their counterparts in the Yaris.

In super slow motion we see all the science in action,

and like all natural phenomena,

it has a beauty and majesty of its own.

Just like the hammer and the can,

it's an inelastic collision.

You can see how the vehicles seem to stick together.

Right before our eyes we see kinetic energy

being transformed into the destruction of both cars.

Then mass appears to win as the Yaris accordions backwards,

but the amazing thing is it hasn't.

(intense music)

In terms of our original question, Chris,

whether you're better off

in the small modern Five Star Safety Rated car

or the much heavier, bigger, older car,

in you're view what's the data saying?

Really clear.

All of the data that we've got from

the video capture through the damage we see in the cars

is the occupant of the little car comes away a lot better.

So kinda hands down winner, little car.

Yeah, definitely.

You want the little car.

Even the high speed video footage we've got shows

that during that impact,

the little car's crumple zones work exactly as we intended.

The squash back absorbed that energy along the way.

Even though when you look at the footage,

the bigger mass of the larger car has pushed in

and pushed the little car backwards,

you'd still rather be in that little car.

At the beginning of the show I posed the question,

as passengers, would my family be better off

in a small modern car or a large heavy old car?

In a collision, size really does matter.

Take speed out of the equation

and big will always defeat small,

but car collisions aren't as simple as that.

Modern safety features mean that even a small car is able

to take much of the impact of a collision without passing

it on to you and your family.

What have we learned?

Well, after all of that,

mass was defeated by science

and technology.

That was a hands down win

to your small modern Five Star Safety Rated car.

(intense music)