All language subtitles for Ancient.Engineering.S01E01.Roads.That.Changed.The.World.1080p.AMZN.WEB-DL.DDP2.0.H.264-NPMS_track3_[eng]

- [Greg] We are surrounded

by extraordinary
feats of engineering.

Constantly pushing the
boundaries of what's possible.

- Without engineering,
there'd be no modern world.

- [Greg] Gigantic cities,

amazing infrastructure,
and ingenious inventions.

- Engineering is the key to
turn dreams into reality.

- [Greg] To reach
these dizzying Heights,

today's technology relies
on breakthroughs made

by ancient engineers.

- It's mind boggling
how they did this.

- [Greg] How did early
civilizations build

on such a scale?

- They raised the bar
for construction in a way

that no one thought possible.

- The sheer engineering ability,

which is in itself impressive.

- [Greg] By defying the
known laws of physics,

and daring to dream big,

they constructed
wonders of the world

from gigantic pyramids,

to awe inspiring temples,

and mighty fortresses.

All with the simplest of tools.

- You know, imagine the skills
people would have needed

to build like this.

- [Greg] Now, it's possible
to unearth the secrets

of the first engineers.

- They managed to
construct edifices

that have survived
the ravages of time.

- [Greg] And reveal
how their genius laid

the foundations for
everything we build today.

[dramatic music]

The wheel and the road.

Put together, perhaps the
greatest engineering development

of all time.

- Roads have enabled
humans to move at speed,

enabled connectivity.

- It's hard to imagine
civilization without roads.

- [Greg] Today,
the planet is alive

with the sound of
rubber on tarmac.

1.2 billion cars,
motorbikes, vans, trucks,

and juggernauts move
us from place to place

on the millions of miles of road

that crisscross the continents.

- The road has been an
extremely important part

of the development
of the human race.

- [Greg] It's one of the
triumphs of engineering,

allowing freedom of movement.

- Roads have enabled humans
to move materials across land

that otherwise would
not have been possible.

- [Greg] Running
through icy wastes,

Amazon jungles, mountain
passes, and deep ravines,

roads shaped the development
of human society.

- The design of the cities
was centered around the car.

- Roads are vital
for the way we live,

and they've changed how we live.

- [Greg] But this global system

didn't emerge fully formed.

The first secrets of road
and transport technology

were cracked thousands of
years ago in the ancient world.

[footsteps]

One early civilization's
engineers have gone down

in history as the greatest
road builders of all time.

Constructing a 50,000 mile
network threaded across Europe,

the Middle East,
and North Africa.

- It was not only very vast,
it was also very efficient.

You can get the troops

to their designated
places very quickly.

- [Greg] Their
technological know-how

and engineering prowess
was second to none.

The Romans.

- Roman road building
produces a network

of communication that is not
just important for the Romans,

but that's going to endure
for centuries thereafter.

- [Greg] Roman
expertise and skills

would inspire generations of
architects and civil engineers.

- They had an
incredible understanding

of structural engineering
that we still build on today.

- It's embedded in
everything that we do

as modern civil engineers.

- [Greg] They developed
groundbreaking techniques

to construct new types of
roads, bridges, and tunnels.

- Without the roads
there wouldn't have
been a Roman empire.

- [Greg] But Roman engineering
skills didn't appear

out of nowhere.

The story of roads
begins much earlier

at the very dawn
of civilization.

Long before avenues, streets,
boulevards, and autobahns,

early humans relied
on simple paths.

The easiest way for
people and animals to move

through the landscape.

But sometimes this
proved difficult

due to natural obstacles
lying in the way.

- Marshy land, boggy land,
potentially treacherous land.

It's not new for people
to want to cross things

that they shouldn't cross.

- [Greg] Could an
important discovery reveal

how ancient engineers found
one solution to this problem?

The Avalon Marshes in
the west of England.

A distinctive landscape
formed over the centuries

by the extraction
of peat for fuel.

And preserved within
this marshland,

a 6,000 year old secret.

In 1970 while
clearing out a ditch,

one peat cutter stumbled
across the remains

of a mysterious
wooden structure.

Tree ring dating revealed
it had been built

and laid in 3806 BC.

- That's the wonderful thing
about dendrochronology,

tree ring dating, is that
you can get yourself back

to the exact winter in the past
when that timber was felled.

- [Greg] The
structure had survived

because peat forms
in waterlogged soils.

With little or no
access to oxygen,

bacteria are unable to fully
decompose organic matter.

The well-preserved wooden
remains are an example

of early engineering ingenuity.

An entire stretch of
prehistoric trackway.

Archeologists named
it the Sweet track

after the peat
digger who found it.

- The Sweet track is an
amazingly neat solution

to a particular problem,

which is how do you get
from one place to another

whilst crossing a marsh?

- [Greg] This remarkable
find turned out to be one

of the earliest road like
structures in the world.

But how had it been built?

- The Sweet track is
a very clever design.

Very simple kind of X shape,

pegs would have been put down
with planks going across,

leading through
this swampy area.

- [Greg] It was a simple

but brilliant
engineering breakthrough.

One that would change the world.

As they've grown, roads have
completely reshaped human life.

In the last hundred years,

the globe has experienced
massive environmental

and economic change,

and road construction
has had to keep pace

with ever growing
numbers of vehicles.

With over four million miles,

the United States has built

the world's largest
road network.

Super highways stretching
from city to city,

state to state, coast to coast.

But solid roads have
been around a lot longer

than first thought,
and one discovery

from the ancient
world would rewrite

the story of the
rise of the road.

[thundering]

It was discovered in the
unlikeliest of places.

Built by a civilization

that seemingly didn't
need roads at all,

as it had command
of a mighty river.

Around 5,000 years ago,

the ancient Egyptians
established their extraordinary

and enduring civilization.

Famous for great advances in
every area of human endeavor,

from the arts to science,
technology to religion,

their accomplishments
include great monuments,

pyramids, temples, and artworks.

Egyptian civilization
developed along the river Nile.

- It was the super highway
running through Egypt.

It gave Egypt life.

- It basically joins
up every single

inhabited place in Egypt.

- [Greg] With all
its towns built

along the Nile's banks,

the river was Egypt
obvious means of transport.

- The Egyptions used ships
for pretty much everything,

so food and drink was
transported by boat certainly.

Building stone was
transported by boat.

People used ferries
on a regular basis.

- [Greg] For many years,

experts thought this
was a civilization

that simply had
no need of roads,

but that was about to change.

In the mid nineties,

while mapping out a
region 43 miles southwest

of modern Cairo,

two American geologists
made an amazing discovery.

They stumbled across a
series of stone slabs

that seemed out of place.

For miles around, there was
nothing but empty desert.

Further studies revealed
these were paving stones.

Although much of its length
had disappeared over time,

the archeologists realized
they discovered a massive road,

seven and a half miles long.

Pottery fragments found nearby
proved it had been built

between 2600 and 2200 BC,

making it the oldest known paved
road anywhere in the world.

Incredibly, it had been
constructed long before

the wheel was first
used in ancient Egypt.

- Yeah the road's an
exciting discovery

because this paved road
is a thousand years

before we think the wheel
is really introduced

into Egypt on chariots,

so why would they
need a paved road?

What was being transported
along that road?

- [Greg] Answers seem to
lie with a nearby quarry.

- The reason why they
went to all the effort

of building this road
was because the stone

from the quarry was a
particularly exotic sort,

you couldn't find
anywhere else in Egypt.

- [Greg] The basalt stone
quarried at Widan-El-Faras

was pulled along the road
to the ancient Lake Moeris,

seven and a half miles away.

There it was placed on barges
and transported up the Nile

to the pyramid
construction sites.

- Yeah, the road's an
exciting discovery,

because it really helped
us to build the picture

on how things like the
great pyramid were built.

- [Greg] As the sands of
time have reclaimed the land,

the road today appears
to lead nowhere,

ending abruptly in the
middle of the desert.

Building a paved route through
such an inhospitable place

was a daunting task
for ancient engineers.

And even today,
road construction

through desert terrain
remains challenging.

[dramatic music]

The Empty Quarter
in the Middle East,

largest sand desert
in the world.

Covering an area of around
250,000 square miles.

In days gone by, only
the hardiest of travelers

would attempt a crossing.

It has stood for centuries
as a natural barrier

between the kingdom
of Saudi Arabia

and the Sultanate of Oman.

Despite the extreme terrain,

the two countries
were determined

to create their
first transport link,

but engineering this desert
freeway would prove every bit

as difficult as crossing
it on foot or camel.

- The temperatures vary from
over 50 degrees during the day,

all the way down to
one degree at night.

- You're building on sand,

and that sand moves
all of the time.

Some of these sand dunes
are 80 meters high,

and so you're building
a road through a desert,

the ground is
moving beneath you.

- [Greg] Overall, 170
million cubic yards of sand

was cleared for construction.

Hundreds of workers
took three years

to complete the project.

Now open, this freeway
has transformed

what was once an arduous journey

to a relatively brief drive.

The modern technology used here,

wasn't available to
ancient engineers.

That didn't stop
early civilizations

building large road
systems of their own.

But for early roads to
become truly effective,

a major engineering
breakthrough was needed.

[upbeat music]

A deceptively simple invention
that would change everything.

The wheel.

It enabled the
creation of vehicles

from simple wagons
to fine carriages,

and chariots of war.

Producing power,
and keeping time.

Giving rise to grueling
challenges and safe landings.

Creating excitement, making
us scream to go faster.

Bringing movement for all.

And even the chance to
explore new planets.

So when did the wheel
roll onto the human stage,

and who invented it?

In 2002, archeologists
were excavating the ruins

of ancient pile dwellings.

Houses built on stilts,
located in marshland

near the city of
Ljubljana, Slovenia.

The team unearthed
a wooden cartwheel.

It was made of ash
and its axle of oak.

Archeologists knew right
away it must be ancient,

but radiocarbon dating
revealed that it was in fact

over 5,000 years old,

making this the oldest
wheel yet discovered.

- Here is a breakthrough moment
in the history of the world

that really does
hold an important key

in terms of the story
of human evolution.

- [Greg] The wheel
was the breakthrough

that allowed roads to
come into their own.

Beginning with simple carts,

this technology
was life-changing.

- And rather than what
you can carry in a basket

on your back, all of
a sudden you've got

the opportunity with
this technology to
move that much more.

- [Greg] The invention
of the wheel drove

an explosion in transportation.

Over time, carts got bigger.

Carriages and wagons
were developed,

capable of carrying
heavier loads,

and moving goods and people
further than ever before.

This simplest of all inventions

has led to a world that
moves at a relentless speed.

Today, road transport
operates on a gigantic scale.

Around 335 million
commercial vehicles,

vans, lorries, buses, and
trucks operate across the globe,

delivering everything
and anything, wherever
it needs to go.

And possibly the longest
delivery route in the world

can be found in Australia.

Highway One stretches
9,000 miles,

and circumnavigates
the entire country.

Some of the biggest monster
vehicles carry goods

along this massive road.

Trucks reaching over 175 feet
long with around 100 wheels.

They're known as road trains.

- They can do that because
the roads are flat and empty,

and they don't have to
stop or start very often

for hundreds of miles,
you know, straight roads.

- [Greg] But when it
comes to straight roads,

one ancient civilization
springs to mind.

Their transport
network was built

upon breakthroughs made
in earlier centuries.

With the wheel in place, and
stone roads tried and tested,

Roman engineers had all
the building blocks.

They brought them together
to conquer and control

the biggest empire the
world had yet seen.

Extending across 5 million
square kilometers of Europe,

North Africa, and
the Middle East.

At its peak, Rome ruled
over 50 million people,

nearly a fifth of the
world's population,

and they simply couldn't
have done it without roads.

- Very hard to talk about
roads and the origins of roads,

without talking
about the Romans.

- [Greg] But what were
the engineering secrets

that made Roman road
buildings so revolutionary?

Roman engineers began
building roads in 312 BC,

the first running
from Rome to Capua,

near present day Naples.

It was named the Appian Way.

- The Appian Way was
Rome's first major road.

It was their highway
down into south Italy.

- [Greg] The Romans developed
new engineering techniques

to construct this
ancient super highway.

Once an ideal path was
cleared, a trench was built,

filled in with sand and boulders

to create a solid foundation,

followed by a layer of gravel
compacted with clay or mortar.

On the surface, a layer
of paving stones angled

to allow the water to
drain off to the side.

This was a road unlike
any seen before.

- It's as technologically
advanced a road

as you're likely to see.

It's got elements of
everything we would do

in a road today.

They had drainage systems,
they had impermeable layers,

they had crushed
stone, dressed stone,

the whole shooting match.

- [Greg] The Appian
Way connected Rome

with nearby cities and
regions, extending control.

But this was only the beginning.

Rome's generals soon realized

the advantages
good roads offered.

- A paved road with 40,000
Legionnaires coming at you

would be incredibly
intimidating.

- [Greg] And it
was Roman soldiers

who built much of the network.

- When you look at the
list of different skills

that were available in the
Roman army, it's a long list,

and included in that
were experts surveyors,

engineers, and
construction workers.

- [Greg] Roads were
constructed on a vast scale,

enabling Rome's
further expansion.

- Having dominated
the whole of Italy,

the Roman imperial
ambition grows greater.

Colonizing neighbor
after neighbor,

after neighbor, after neighbor.

- [Greg] Between
200 BC and 14 AD,

Roman armies invaded
most of Western Europe,

Greece, and the Balkans,
the Middle East,

and North Africa, all linked
by newly constructed roads.

- We say all roads lead to Rome,

and for the Roman road network
this was definitely the case.

- [Greg] This extensive
network allowed Roman troops

to quickly March
to trouble spots,

even at the farthest
reaches of the empire.

- So you can move say
from Rome to Britain

in tens of days, which is very
fast by ancient standards.

- [Greg] This
sprawling road network

would also help
create vast fortunes.

- The better the
roads, more of them,

over longer distances,

the more material
can be moved around,

the more sales, the
more contracts, and
the greater wealth.

- [Greg] The Romans
even built roads

across some of the
most hostile terrain.

Terrain that even today presents

a major challenge for engineers.

The mountains of Norway.

Roads here are often
narrow and twisting,

thanks to the extreme landscape.

So when planners decided a
new, bigger route was needed

to link Bergen in the west
with Oslo in the East,

they faced a problem.

They'd have to cut straight
through a mountain,

calling for the longest
road tunnel in the world.

[dramatic music]

So how did engineers
go about building it?

The solution came
from outer space.

High tech satellites
orbiting the earth.

- The tunneling machines
operate completely independent

from humans, so they're
guided by GPS systems

that position them precisely,

even though they're
below the ground.

- [Greg] A staggering 3
million cubic yards of rock

was excavated from the tunnel,

but construction wasn't

the only complication
engineers faced.

In a tunnel taking 20
minutes to journey through,

how could they deal
with driver fatigue?

- One of the design solutions
was having the road moving

from straight to curved,
straight to curved,

to keep the driver having to
move the wheel and stay alert.

- [Greg] Designers and
psychologists experimented

with lighting levels.

They divided the tunnel
into four sections,

separated by three
large mountain caves.

While the main tunnel
has white lights,

the caves have blue and yellow.

- This was to counteract things

like claustrophobia or panic,

keeping people calm
in such a long tunnel.

Using this creative
blue and yellow lighting

to simulate almost
like a sunrise,

and keep people calm and
content in their journey.

- [Greg] This clever
tying together

of engineering and psychology,

allowed engineers to
build the impossible.

The tunnel opened
in the year 2000,

having taken five
years to construct.

Back in the ancient world
without modern machinery,

tunneling through a mountain
was almost unthinkable.

Even the Romans were forced

to compromise their
famously straight roads,

but there's one other
natural obstacle

that Roman engineers had no
choice but to tackle head on.

Water, sometimes there's
no way around it.

- The classic Roman road
was entirely straight,

entirely level,
marching out like a set

of legionaries
across the landscape,

and that does produce problems

when you encounter a river.

- [Greg] For centuries,

earlier civilizations had
built short foot bridges,

but for Roman generals
to march thousands

of Legionnaires across a river,

something much more
substantial was required.

If Rome was to
continue its expansion,

it was vital engineers
crack this problem.

To build permanent
stone bridges,

the Romans needed
new technology.

- The technology they use
to build these bridges

is really quite something
when we think about

how long ago lots
of these were built.

We have some brilliant examples
all over the Roman empire.

- [Greg] Some Roman bridges
even survive to this day.

So what were the secrets
of their construction?

In search of answers,

scientists analyze the chemical
makeup of Roman mortar.

They discovered it was
a strange concoction

of volcanic ash,
lime, and water,

mixed together
with volcanic rock.

Experiments show that as
the volcanic ash binds

with limestone, a chemical
reaction takes place.

This prevents the spread of
cracks within the concrete,

making it stronger.

- The resulting
concrete that they made

could actually set underwater,

and that was a really special
feature of Roman concrete.

- [Greg] With this breakthrough,

new kinds of construction
became possible.

Rome's greatest
engineers set to work.

Among them, Marcus Vitruvius.

- So Vitruvius was one
of those classic examples

of the master builder,

and he wrote this incredible
series of 10 books

about how to build things.

- [Greg] These works
have guaranteed his place

as one of the greatest
architects in history.

- Vitruvius says that
when we design something,

any building at all, we have
to consider three things:

strength, function, and beauty.

- [Greg] Waterproof concrete

gave Roman bridges
solid foundations,

but how would Vitruvius
and his engineers

build bridges strong enough
to support the weight

of an entire Legion
marching across?

- When you put weight on
something, you bend it.

And when you bend it,

the top of that piece
of steel, or concrete,

or whatever it might
be, is in compression,

and the bottom is in tesion.

Tension is what rips it apart.

[scream and crash]

- [Greg] Once again,
Roman engineers improved

on an earlier design.

- They created this magical
structure called the arch.

The entire structure
is in compression,

and so that meant they
could just use stones,

and if you pile stones
up in an arch shape,

you can put a huge
amount of force on it.

- [Greg] Bigger arches boosted

Roman construction capabilities.

- This arch structure, which
enables you to build up,

as well as out, of
course is fundamental

to not just the construction
of bridges and aqueducts,

it's also going to be
important in the construction

of civic buildings, like the
theaters, the amphitheaters,

and even the Colosseum in Rome.

- [Greg] The combination
of Roman concrete

and the Roman arch made these
structures incredibly robust.

An astonishing number
are still in use today.

The Alcantara Bridge over
the river Tagus in Spain

was built between
104 and 106 AD.

A Latin inscription on
one end of the bridge

boasts of Rome's
engineering prowess.

[speaks foreign language]

- Which means I
have built a bridge,

and it will last forever.

Very Roman, and so far so
good, it's still there.

- [Greg] But the Romans
aren't the only civilization

to have built
impressive bridges.

Inspired by their
Roman predecessors,

modern day engineers continue
to push the boundaries.

[upbeat music]

- Bridge design today is a
really, really exciting thing

to do as a structural engineer.

There are so many different
materials being used

at the moment.

There are so many
different forms

that the bridges
can take as well.

And to pick a favorite bridge,

I think I'm gonna go with
the Golden Gate Bridge

in San Francisco.

- [Greg] The golden
gate bridge was opened

to traffic in 1937.

Its main span is
4,200 feet long.

The US Navy had wanted
the bridge to be painted

in blue and yellow stripes
to increase its visibility,

but when the steel
arrived in San Francisco,

painted in a burnt red primer,

the consulting architect
decided the color

was more pleasing to the eye.

For nearly three decades,

this was the longest main
suspension bridge span

in the world.

- Some of the big
suspension bridges

that have been done
are just jaw-dropping.

- [Greg] The record is now held

by the Akashi Kaikyo
bridge in Japan,

just under 2.48 miles long.

[upbeat music]

It stands in an
earthquake prone region.

It also gets hit by some of
the Earth's most severe storms.

[thunder and wind]

It's built to stand winds
up to 180 miles per hour.

Piercing the sky
above southern France

is the tallest
bridge in the world.

The Millau Viaduct
enables motorists

to take a drive through the sky,

890 feet above the Tarn Valley.

[upbeat music]

But modern engineers
haven't always got it right.

- Every now and again,
a disaster happens

that makes engineers
stop and think about

what they're doing.

- [Greg] July, 1940.

The Tacoma Narrows Bridge,

built in the United States of
America, was open to traffic.

At that time, it was the third
biggest suspension bridge

in the world.

- So the Tacoma Narrows
Bridge was built

in an era where bridge
designers were really starting

to push the limits
of what was possible,

and suspension bridges
were all the rage.

- At that time, the
understanding of the
aerodynamic effects

on these very
lightweight, slender,

flexible bridges was
not well understood.

- [Greg] The Tacoma Bridge
had a fatal engineering flaw.

Shortly after its construction,

it started to buckle and
sway along its length

in windy conditions.

- The bridge got
excited by the wind.

The frequency of the wind,

and the frequency of
the bridge was similar.

And just like a tuning fork,

the bridge actually started
dancing on the wind.

- [Greg] It soon acquired the
nickname Galloping Gertie.

And just four months
after opening,

on a stormy winter's
day, disaster struck.

[intense dramatic music]

- As it was dancing,
it tore itself apart.

[crash]

- It absolutely blows your mind

that this bridge was
made of concrete,

because it just looks
like paper flapping away.

- And that was an absolute shock

in the world of engineering,

that such a sophisticated,
leading structure, could fail.

- [Greg] With any
new technology,

failure is always a possibility.

But engineers learn
lessons from each mistake,

and continuously
improve their designs.

A process of trial and error,

that also applied in
the ancient world.

[rumbles]

The earliest wheels were just
crude round lumps of wood.

Result, slow
cumbersome vehicles.

- The big issue with
the big solid wheel

is they're really heavy.

The poor old oxen, or whatever
it is pulling the cart,

has got to deal with wheels

that may weigh
more than the load.

- [Greg] But the wheel
got a major facelift

around 2000 BC.

Engineers figured out that
replacing the middle portion

with spokes would
retain strength

while making the wheel lighter.

- The primary
benefit of the spoke

is that it reduces the
weight of the wheel.

- [Greg] The spoke
enabled new types

of vehicles to emerge,

faster and leaner
like the chariot.

An icon that helped
define the Roman empire.

Most have been lost to
the ravages of time,

but one amazingly intact
example turned up in 2019,

on a burial mound in Croatia.

Just under 2000 years ago,

this site lay within the
Roman province of Pannonia.

The find was a sophisticated
two wheeled carriage,

revealing the engineering
mastery of the era.

And alongside the
vehicle, intact bones.

- There was a Roman chariot
found buried in Eastern Croatia

that also included human
remains in the site,

and the remains of horses.

- [Greg] It was spectacular.

Shining a light on Roman
advances in vehicle design.

- The chariot is
hugely important.

It enables you to
travel farther,

and faster, and better than
any other form of transport.

The chariot's also a
significant symbol.

It literally lifts you
up above the people

who were walking around you.

And so to be buried
with it in death,

is to prove how important
you were in life.

- [Greg] But these vehicles
weren't just status symbols

for the Roman elite.

They were first and
foremost for racing.

- Chariots for the
Romans were something

to be used in a spectacle.

- [Greg] And there was
only one place to go,

the Wembley stadium
of ancient Rome.

The Circus Maximus.

Largest stadium in ancient Rome,

the Circus Maximus was built
solely for chariot racing.

It was constructed around
the sixth century BC.

- At a capacity, the crowd
seemingly of 250,000 people

all assembled to watch
teams of charioteers racing

at high speed, with high danger.

It's one of the great,
great, great sights of Rome.

- [Greg] The racing
chariots were lightweight,

but very sturdy.

The wheel base was wider
to minimize the risk

of rolling over, and
smaller wheels decreased

the force on the
spokes when cornering,

though this led to a more
bumpy ride for the charioteer.

[upbeat music]

- The Circus Maximus is
basically Silverstone,

or Monte Carlo for the Romans.

- [Greg] Just as the ancient
world sent out charioteers,

their modern day equivalents
still take to the track today,

in vehicles that reach
extraordinary speeds.

Drivers pit themselves
against each other

in the lightest and fastest
cars engineers can build,

with speeds approaching
nearly 300 miles per hour.

The technology is so advanced,

some change gear quicker than
the blink of a human eye.

- These are the fastest
vehicles on earth,

and they're made of
really light material,

they have huge downforce.

They're incredibly aerodynamic.

But they only work because
those aerodynamics work

with the surface below.

- [Greg] Just like
motorsports today,

with their promise of
excitement, danger,

and occasional catastrophe,

[crashing]

ancient chariot races were
also an adrenaline sport.

Races were grueling.

Seven laps covering a
distance of around five miles,

lasting up to 15 minutes.

- Life of a Roman charioteer
was a very dangerous one,

and your life expectancy
was extremely short.

- [Greg] The final races
in the Circus Maximus

were held in 549 AD, almost a
millennium after they began.

By then the Roman Empire
in Europe and North Africa

was falling into
serious decline.

Rome was losing
its grip over many

of its conquered territories.

Despite its massive
road network,

the Empire had
become overextended.

- The Romans didn't
really have the resources

to keep control of such
a huge area of land.

- The Roman Empire falls,

the Roman roads
fall into disrepair,

and the terribly complicated
system of constructing them,

maintaining them, and
using them, falls away.

- [Greg] Romans may have
stopped building roads,

but across the world,

other empires were expanding
or creating their own.

China continued its period
of road construction

at this time.

And the Incas began building
their impressive road network

during the 15th century
in South America.

But in Europe, for well
over a thousand years,

no one bettered Roman
road building or design.

- Roman roads are still
used in the middle ages.

You get a patching
up, you get a repair,

you get a reuse of Roman roads,

and a reuse of the technology.

- [Greg] And have Roman
roads left a legacy

that shapes our way
of life even today?

Clues to their impact
were discovered

by a team exploring
satellite imagery

of modern European roads.

Satellites orbiting the
earth capture images

of every part of the
planet day and night,

and a recent study compared

modern Europe's
nighttime illumination

with a map of the Roman
road network at its peak.

[dramatic music]

- So when researchers map
on where modern roads are,

compared to their
Roman predecessors,

they match up
extraordinarily clearly.

- [Greg] Nearly every junction

from the ancient Roman
roadmap is matched

by a splash of light
in the modern era.

Evidence that modern
European cities and motorways

were built upon roots
laid down by the Romans.

Roman roads formed the backbone

of the continent's road systems.

- The legacy of Roman
territorial conquest,

Roman power, is still
ingrained in our earth today.

Across Europe, we still
use the same sort of roots,

we still live in towns
that were founded

or occupied by the Romans.

- [Greg] It took
many years for Europe

to surpass the peak of
Roman road building.

By the 18th century, with
Europe's wealth increasing,

demand for improved
transport was growing fast.

- As more vehicle traffic
came on the roads,

they had to be wider.

And when widening the roads,

that meant a new era of road
construction had to begin.

- [Greg] Yet it wasn't
until the latter part

of the 18th and
early 19th century

that engineers created the
first truly modern road.

And it was a British
engineer, John McAdam,

who made the breakthrough.

He was convinced that massive
stone slabs were unnecessary

to support the weight
of passing carriages,

so long as the road
itself could be kept dry.

- McAdam actually said, "We
don't need those big lumps

"of stone at the bottom."

And to compare it with
the Roman technology,

I mean the Roman roads
were six foot thick,

and these things
was two foot thick.

- [Greg] His design
resulted in improved roads,

built faster and at lower
costs than ever before.

The technology quickly
spread across Europe

with the majority of main roads

undergoing McAdamization by
the end of the 19th century.

And this new road engineering
came in the nick of time.

There was a new
kid on the block,

about to roll off
the production lines

that would change
society, economics,

and civilization forever.

The ultimate freedom machine.

Horse powered
transportation had been king

of the road for 5,000 years,
but now it's reign was over.

- There is a massive,
massive change,

and one we are still
living with today

with developments in the
internal combustion engine.

[upbeat music]

- Since the Romans,
speed of travel on roads

has not changed.

It's people walking,
is herding sheep,

and it's horse-drawn carts.

Along comes a car and
all of the sudden,

in a period of a decade,

you've moved from nought
to 10, to naught to 30.

In another couple of
years, it's naught to 50.

- [Greg] As car
production increased

throughout the 20th century,
so did road building.

- What the motorcar
enables you to do

is to go from
exactly your doorstep

to someone else's doorstep,

and that's not just
for personal travel,

but that's for the
movement of goods as well.

- [Greg] Across the
world in every country,

on every continent,
networks of roads became

the living veins
of modern society,

reshaping cities and landscapes.

- The idea of the
road and the car

begin to dominate city planning,

and you have cities
built around the idea

that everyone goes
everywhere in a car.

- What that does is
to produce a demand

for ever bigger, ever
longer, ever wider highways,

when every time you
construct a new highway,

more people buy cars,
because more people are able

to take advantage
of that freedom.

- [Greg] The car may
have made life easier,

but reliance on
these metal beasts

has come at a terrible price,

[dramatic music]

as the planet chokes on the
exhaust fumes cars leave

in their wake.

- It has created problems for
our planet through pollution,

CO2 emissions,
methane emissions,

and greenhouse effect of course.

- [Greg] Road traffic accounts

for over 20% of
global CO2 emissions,

and road construction
adds to that.

Roads and cars are considered
a major contributor

to global warming.

And in many places,
road transport

has become an urban nightmare.

Manila in the Philippines,

and Bangalore in India,

are considered to be the
worst places on the planet

for traffic congestion.

In many cities, it's now
quicker to cycle than to drive.

With the world facing
massive environmental damage,

engineers are now stepping up
to help reinvent the wheel,

and the road.

Fleets of electric cars
controlled by computers

may one day automatically select

the most efficient
available routes

on roads which provide
their own power supply.

- One idea is that roads will
become large solar panels,

so the roads themselves will
absorb the sun's energy,

and then they'll put that energy

into the electric vehicles
that drive on them.

- [Greg] But new
technology may not solve

all the problems of
overcrowded roads.

- The future must be finding
a way of continuing to travel,

continuing to trade,
continuing to communicate,

but doing so leaving a
less dangerous footprint.

Finding a way that
doesn't cost the earth.

- [Greg] From the early
trackways of stone-age Britons,

to the paved roads
of ancient Egypt,

the road network of
the Roman empire,

to modern super highways,

the road has long been the
driving force of humanity.

Throughout the
centuries, road engineers

have built big, dug
deep, and scaled heights.

Inseparable, the road and
the wheel have endured

a long journey to what
they have become today.

The wheel had a rough start
as a clumsy heavy contraption.

It's evolved into
a fit lean machine,

transporting people
further and faster

throughout the globe
than ever before.

From the very beginning,
human ingenuity and innovation

has overcome the
greatest of obstacles.

Ancient engineering
was essential in
laying the groundwork,

and whatever the future holds,

it'll be engineers who keep
the planet on the move.

[intense dramatic music]