Original subtitles

All over the world, one of our railroad's most impressive feet is

nature's great divides.

This is an extremely busy waterway.

There are thousands of boats that go through.

From deep river gorges to wide open seas, these impossible

crossings create engineering challenges that could stop a railroad in its

tracks. If we leave it very much longer, it will fail.

Requiring ingenious solutions.

For me, it is the masterpiece of engineering.

I love it.

They make the impossible possible.

I may say a little bit, but it's awesome.

From the world's wildest waters to its mightiest mountains,

railroads have set out to conquer them all.

What a feat of engineering.

Absolutely amazing.

Driven by daring engineers for whom no obstacle is too great.

I truly love this structure. It's magnificent.

Staten Island in southwestern New York.

Sandwiched between mainland New Jersey and Brooklyn, it's a critical gateway

into this busy metropolis.

One which trains must access.

Today, alongside tons of cargo, Professor Eric Lima is experiencing an

view of the railroad.

Oh man, we're on the front of a diesel train right now.

The power on this thing is amazing.

This freight service is huge for New York.

But getting locomotives into Staten Island means overcoming a tricky

geographical problem.

It's the artery that brings... All of the goods and services that we use on a

daily basis, and we don't think about it when we're in the city, but New York

City is completely surrounded by water.

So for trains, this is easier said than done.

In New York, the stretch of water separating Staten Island from New

known as the Arthur Kill, may only measure around 560 feet across.

But it's packed with both.

This is an extremely busy waterway. There are thousands of boats that go

through. And if you're going to have a railway across, you're going to have to

have clearance for those boats to go under.

For a pedestrian or car bridge, getting this clearance is no problem, as rubber

tires and soles can cope with an incline.

But steel -wheeled trains faced with a quick ascent can start to spin.

In 1959, the Baltimore and Ohio Railroad found a monumental solution to this

problem.

Wow, this is amazing.

It's the world's largest lift bridge, the Arthur Kill.

But it's this bridge's extraordinary actions, rather than its colossal scale,

that makes the Arthur Kill Bridge a standout structure.

I mean, that's an engineering marvel.

With a lift span of almost 560 feet, the Arthur Kill is the longest single -span

vertical lift bridge in the world.

When lowered for train... It clears the water by 30 feet. But when raised, the

fan towers 135 feet high, leaving clearance for even the biggest shifts.

here at the AK Bridge, we have the bridge drop scheduled for 9 .45 a .m. Do

see any problems with that as far as vessel traffic goes?

But for Supervisor of Structures, Ryan J. Wagner, it's not all smooth sailing.

To minimize disruption, the bridge can only be lowered three times a day for

just half an hour.

Okay, yeah, I see. She's coming northbound, right?

I'll call when I know she's clear, all right?

Okay, roger. Will do.

For our bridge drops here, we have to coordinate with the Coast Guard based on

the tremendous amount of vessel traffic coming through the Arthur Kill Channel.

We have about a half -an -hour time frame to get the train over and then to

the bridge back in the fully open position.

Lowering and raising a 2 ,200 -ton lift span in such a short window requires

supersized engineering.

The bridge is fitted with a powerful system of counterweights and cables,

by motors installed at the top of each tower.

Security, security, security, AK railroad bridge coming to a close.

Security, security, security, AK railroad bridge coming to a close.

With all shipping being kept at bay, Ryan is putting this cutting -edge

technology into action.

I've enabled the controls.

That's enabled power to go to both drive motors. Once the drive motors are fully

energized, I give the command for the bridge to go into the span seated

position, and then the bridge starts coming down.

All right, here we go. It's starting.

The concrete -filled steel boxes used as counterweight.

Each weigh an enormous 1 ,100 ton.

You can see the counterweights moving up right now in the perfect balance to the

bridge that's coming down.

You really want the bridge to come down exactly level.

Both the motors have to work simultaneously, and so that there's no

trains can go across, and then we can go across.

After just two and a half minutes, The span enters its final leveling, a

critical phase demanding millimeter precision.

So right now you have the bridge going through its skew correction system. We

have a variety of sensors that are basically detecting all kinds of

gearing, physical track structure like the rails.

If the tracks don't line up, the trains will miss their crucial slot.

If all those checks are not correct, the dispatcher will not be able to allow a

train to pass over the bridge. That caused a variety of issues.

Train delays, it impacts vessel traffic because now we have the bridge seated

and it cuts into our half an hour time frame.

With the bridge successfully locked, now the goods trains and Eric can carry on

their journey.

All right, we saw it come down.

and now we get the pleasure of actually going across it. What a piece of

engineering. I'm looking at it now. I see the giant counterweights above.

We're on it seamlessly.

You can hear the banging and the clashing, and I see the water

What a brilliant bridge.

It's really hard to imagine that this is actually 100 feet higher in the air on

a normal basis.

The 560 -foot shortcut between New Jersey and Staten Island takes a matter

seconds.

The race is now on to get the waterway moving.

Roger.

So right now we're starting the process for the bridge opening.

You have the warning indication to notify anybody that's on the span that

bridge is going to be opening.

Ryan and his team now have less than three minutes to open this impossible

bridge.

See the counterweight coming down right here right now.

So at this point now the span and the counterweight are approximately the same

elevation.

Over 50 years after it first operated, the Arthur Killed Bridge still manages

return to its open position right on schedule.

Every day, there's always something new to be learned.

There's always something that can be improved upon in terms of its operation

make it more efficient.

Yeah, it's certainly something that I enjoy working with.

Every day, the ingenious mechanics of this towering bridge allow tons of

to be carried in and out of Staten Island.

Without it, there would be no crossing.

But with this bridge, the train just went right across.

It seems so simple, and yet it's an engineering marvel, and it's really,

gratifying to see it work.

But getting trains across the world's great chasms demands many different

solutions. To get the train across this massive gorge, this would have to be a

bridge of epic proportions.

dreamt up by the engineers of Impossible Railroad.

Nestled on the east coast of New Zealand's North Island lies the Mohaca

Gorge.

Its extreme landscape is perfect for outdoor adventures.

But you would think its towering ravines and fast -flowing river would put the

brakes on any railroad.

But one bridge builder proved otherwise.

Hey, buddy. How's it going?

Good, good, good.

Let's go.

Chuck a life jacket on there, like a backpack.

Make sure you get all four buckles up, including the one right down the bottom

there. For heritage advisor Karen Astwood, there's only one way to

how engineers traverse this impossible chasm.

So this is the Mohaka River, and when you look up, you get a really good sense

of the huge challenge that the engineers had here.

To get the train across this massive gorge, They had to put up a structure

was 350 feet tall, making it the highest in Australasia and the fifth tallest in

the world at the time it was constructed.

This would have to be a bridge of epic proportions.

And here it is.

This is the Mohaca Viaduct.

That is a truly impressive structure.

What a stunning piece of engineering.

I'm actually a little bit speechless.

It's awesome.

It's really great. I love that structure.

Spanning around 980 feet across and 312 feet high.

The Mohaca Viaduct has conquered nature.

Not only is the Mohaca Viaduct a thing of beauty, the engineering that made it

possible is just as impressive.

Completed in 1937, this was a bridge born from an isolated community's

need.

On New Zealand's North Island, the town of Waira sits on the northern shore of

Hawke's Bay, herds on the mouth of a major river.

A wild landscape that 80 years ago posed many problems.

Waira could be often cut off from the rest of the world for weeks at a time

because the basic dirt roads became impassable and bad weather.

And also there's a treacherous sandbar out there in the river mouth, making it

difficult for even the smallest vessels to access the town.

A rail connection to the city of Napier, 50 miles to the south, and Gisborne to

the northeast, would offer Waira a crucial lifeline.

But construction of this vital link was complicated by a series of shattering

setbacks. and the immense engineering challenges posed by the North Island's

rugged terrain.

And no challenge would be greater than the deep ravines surrounding the Mohaca

River.

But engineer John Cull believed he could beat the odds with his design for a

prefabricated supersized steel structure.

Work started in 1930.

With concrete foundations in place, a death -defying workforce carefully began

its construction high above the valley floor.

But the real engineering challenge was getting 2 ,090 tons of steel to these

dizzying windswept heights.

If you can imagine these two ladders are towers either side of the gorge.

Then a cableway was strung across the gorge like this.

Suspended from the cable way, represented here by these carabiners,

which moved independently along like this.

What this meant is that once you had attached a steel component to the crane

hook, like so, it could be moved out into the gorge.

It could then be manoeuvred into place and affixed really quickly.

The engineers took this remarkable solution one step further, flinging two

cables across the ravine, each one working independently, allowing super

steel components to be twisted and swung, positioning them with pinpoint

accuracy.

And because the steel components were prefabricated and then brought to site,

the viaduct could be assembled like a giant Meccano set, and progress was

really, really quick.

Incredibly, Cole's rail bridge was completed ahead of schedule and for half

estimated cost.

The Mohaca Viaduct was the final link in the line to Waira, allowing goods and

residents in and out of the once isolated region.

Today, Waira was totally transformed.

Thanks to one of the world's tallest railway bridges, this once largely

inaccessible town has been given a whole new life.

Creating super high spans is a huge achievement.

But when it comes to crossing chasms, railroad engineers often face an equally

taxing problem.

Fast flowing water.

Whether traversing channels or seascapes, trains often have to

crossings.

And it was one such problem affecting Scotland's capital, Edinburgh, during

19th century.

For this booming city, open countryside to the south and west allowed easy

access for trade.

But to the north lay the Firth of Forth.

A vast estuary renowned for its harsh weather and fast -flowing waters.

For a railroad to overcome this would take a crossing like no other.

The fourth bridge.

The largest steel structure the world had ever seen.

Spanning one and a half mile, 58 ,400 tons of steel and six and a half

million rivet ensures this feat of engineering stands strong against the

battering of the North Sea.

The engineering that was involved was the very best of its day.

The forefront of engineering, the very best of materials.

and we ended up with a magnificent bridge.

It's the brainchild of engineers Benjamin Baker and John Fowler, who

improbable challenge of an 8 ,200 -foot -long bridge with a game -changing

design.

Their solution, based on balance, was to cantilever the bridge.

Three giant diamond -like structures act as center points for cantilevered arms.

A concept best appreciated from an unrivaled view above, as Senior Project

Manager Ian High explains.

Where we are just now is on the tower, one tower of the bridge.

And from each tower, there are two cantilevers.

Effectively like one arm poking out in either direction, stretching out. And

these two arms are what's called a balanced cantilever.

So each balances that other one off.

But it wasn't just the scale of the Firth of Forth that created problems.

In 1879, its predecessor, the Tay Bridge, succumbed to a major storm.

Its collapse tragically killing 75 on board a crossing train.

To withstand the Firth's fierce weather and fast -flowing waters called for rock

-solid foundations.

But in the deep estuary, this was far from easy.

If you can imagine the space between the water to the deck level, you've got

that same depth of water below there.

So it's incredibly deep water.

It's deep in the North Sea, a lot of it.

Building 12 mammoth cylindrical concrete foundations here would be far from

straightforward.

What the general public see, It's actually very top end. If you think of

iceberg, there's a huge amount of work below this actual masonry here.

This is the top of a foundation that goes down 30 feet into the actual bed

itself. And that's where the caisson was used to actually create the foundation.

The caissons were gigantic twin -walled cylinders floated out and sunk in the

estuary.

Once pumped out, 20 to 30 men would then excavate the seabed.

creating the foundations.

With the underwater works complete, Baker and Fowler constructed enormous

to take the weight of 2 ,200 -ton trains and over 55 ,000 tons of steel.

These piers take an enormous load.

All the load of the bridge has to come down onto each of these four points on

each of the three towers.

The most important part of the whole bridge.

As with everything on this impressive bridge, the solution was supersized.

This is a very special place on the bridge.

There's basically very few people have actually been allowed to stand here.

Each one of those blocks of stone is a ton.

So multiply that by several thousand, that's the scale of one of these

foundations. of which we are 12 right through the bridge.

Paul and Baker were at the very forefront of engineering ingenuity.

To even imagine a bridge such as this was in many ways risky.

Has the risk paid off?

No question at all.

Absolutely.

Building the fourth bridge is a feat of railway construction.

But ensuring it stands the test of time also pushes engineers to their limits.

In this part of the bridge alone, we have 190 repairs.

The size of this thing, they're constantly playing catch -up. The race

keep the force bridge safe.

Scotland's birth of fourth.

Home to the staggering one -and -a -half -mile -long Forth Bridge.

Designated a World Heritage Site, this game -changing cantilevered structure is

engineering on an epic scale.

That basically was one Eiffel Tower, so have we got six Eiffel Towers?

I think we have.

Completed in 1890, its jaw -dropping size is down to a pioneering use of

which, unlike its iron -built contemporaries, is super strong,

was once the world's largest bridge.

Guys, what we're going to be doing this morning is we're taking the safety net

out. Today, however, the 58 ,400 tons of steel create an ongoing battle for

consultant coatings inspector John McDonald.

Biggest problem is dropped objects can't happen. Okay?

Everybody happy with that? Yeah.

All right, great.

Salt water and 87 -mile -per -hour winds relentlessly take their toll.

We need to put a scaffold in.

to give access to a steel worker to come in, to do some cutting for us, to do

some welding.

With 200 trains a day passing above, it's crucial this engineering team

maintains the bridge in perhaps the nation's most precarious workplace.

The net is at the moment tied firmly to the bridge, and we're just untying it so

we can start to deploy it. It's kind of a curtain system that opens it up.

So, should we unfortunately drop anything, it will land inside the net.

We're

good

on this side.

Although 95 % of the bridges' steel still exist, the race is on to remove

unsound metal.

In this part of the bridge alone, I think we have scheduled 190 repairs.

They're all small scale, but put together, that's quite a lot of work.

The repair itself might take two hours, but the logistics of getting to the

repair, we could be looking at four or five men working for a week.

And today, like practically every other day, action needs to be taken.

We have two pieces of steel make up this component.

This one is in very good condition, except for a bottom corner here, we have

just a great deal of corrosion.

So we're reaching a point where if we leave it very much longer, this part of

the member will actually become detached from the bridge.

It will fail.

We're going to do the repair.

This is a very small repair.

But eventually you would start to affect the integrity of the bridge if we

didn't do these repairs on a regular basis.

And it will be replaced with a new insert welded in place.

But perhaps this bridge's biggest challenge is seen through its iconic

How many coats is this, Peter?

Second coat.

I'll miss on that one.

Yes. Okay.

John and his team must keep almost 2 .5 million square feet of protective red

oxide paint in good shape.

Squads of men go to a select area, chip away, paint, move on to another area,

chip away, paint, because the size of this thing, they're constantly playing

catch -up.

But now a new solution, developed from the North Sea oil rig, is brushing away

this problem.

On a microscopic scale, it has flakes of glass suspended in the paint.

When it's applied, as it cures, these tiny bits of glass settle down

flat onto each other, a bit like the scales of a snake, and make more or less

glass cover over the steel, impermeable.

25 years, safeguarding the future of this magnificent railroad crossing.

This bridge is in better condition than it has been for the past 75 years,

possibly in the best condition it's been in since it was built.

Sometimes you just stand back and look at the structure and think to yourself,

it's a privilege to be here.

I came along here for six months and stayed for 23 years.

I just love it to a bit.

For any railroad bridge to remain standing, keeping it in top condition is

crucial. But the key to any super strong structure is getting its design right

in the first place.

In Germany, one rift in the landscape... pushed engineers to their limits.

This bridge is an amazing piece of engineering.

The Gulch Valley in the German state of Saxony is a spectacular sight.

at just over 1 ,600 feet wide and 230 feet high.

But as Professor Lutz Niedner is finding out, in the 19th century, it was also a

seemingly impossible hurdle for the railroad.

In the beginning of the 1800s, the engineers had a task to build a new

connection between the towns Leipzig and Hof, and their problem was to cross

this valley.

It's a very huge valley and the valley sides are very steep. So the trains of

the time had the problem that they hadn't enough friction on the rails.

Heavy steam engines of the day struggled on any significant floats.

So building a line down into the valley was out of the question.

A bridge was the only answer.

This bridge has to be a very enormous span and has a very enormous... load

capacity to hold all the trains rolling on them.

The bridge would be unlike any other in the world.

And even today, for those that cross it... After the corner,

we cross the bridge.

This railroad's mind -blowing solution still takes the breath away.

It's a very nice picture, driving over the bridge.

I'm lucky.

This is the greatest bridge in Europe.

The Gulch Viaduct is the largest brick -built bridge in the world.

The simple solution is always the best.

That's what you can see here, the Gulch Tower Viaduct.

Stretching almost 1 ,900 feet across.

and towering 256 feet high.

When opened in 1851, it was the tallest railroad bridge on the planet.

For me it is a masterpiece of engineering.

I love it.

The bridge's extraordinary dimensions are down to one man.

engineer and mathematical genius Johann Andreas Schubert.

He knew that spanning such massive distances while taking the strain of a

could only be achieved by one simple shape.

Schubert was the first engineer who proved the stability of his

a mathematical way on the paper.

He relied on the mathematical principle of an arch shape.

For centuries, the strength of this classic shape has defied belief,

allowing buildings and even the most surprising everyday items to withstand

incredible loads.

On the first side, an egg seems to be a very fragile thing.

If you tap it on a hard surface, it can be easily broken.

If you can see here, the egg is shaped like an arch.

And we want to try to stack some bricks on them.

So this is the crucial point.

The load from the brick is distributed to the four edge shells.

Let's see what happens if we stack another one on it.

So we have just doubled the forces in the shells of the egg.

Let's see if there is a third brick.

The total load of all these bricks is concentrated on the four points of the

eggshells. The load is distributed through the compressive strength of the

of the egg onto the table.

That's what we have in the bridge behind me.

The arch shape is an essential element of civil engineering.

With the load -bearing capacity of arches proven time and again, Could they

withstand lateral pressure like that from a train?

Schubert created a mathematical formula proving they could do just that.

Schubert's formula has a very great effect on bridge construction in that

because he was able to prove in a mathematical way.

that such a simple design has a very high load capacity to carry rolling

on top and to transform these tensions into compressive ones.

Safely crossing trains across the enormous Gulch Valley would take 81

built over four stories.

An elaborate design, which also had to be built on a budget.

Sourcing materials locally.

Schubert's solution was to build with bricks, an inexpensive and easy option

with clay pits in the area.

It was quite unusual in that time to use bricks for such enormous constructions

because bricks don't have so much compressive strength.

So what you need to do is to combine a lot of them so you have a lot of area to

put forces through.

It would take over 26 million bricks to span the chasm.

A normal worker would have to do 1 ,600 bricks a day. And this is a very

challenging work.

After six years, nearly 2 ,000 workers finally completed this record -breaking

structure in 1851.

Looking from this point, I feel very small compared to this massive bridge.

This chasm crossing still stands up to modern engineering, as intercity trains

traveling at over 62 miles per hour glide over its historic arches.

It is incredible what has been built 165 years ago.

This bridge is an amazing piece of engineering.

History's bridges are undoubtedly pioneering.

But the challenges for today's engineers are staggering.

It's difficult to build because we have 16 kilometers from Denmark to Sweden.

When creating impossible railroads.

Many of the world's greatest crossings have been built for the railroad.

Straddling deep gorges.

Traversing wide open valleys.

Keeping our journeys on track.

But sometimes the obstacle can appear insurmountable.

The Orison Strait.

An immense waterway.

forming a natural boundary between Denmark and Sweden.

With its notoriously busy shipping channel and close proximity to an

it's the last place you'd expect to find a railroad crossing.

For centuries, it was only possible to cross by boat, and even that isn't easy.

We have 16 kilometers from Denmark to Sweden, and during wintertime, for

example, you can have ice in this area.

We've had up to 40 centimeters of ice, so you can actually not go by boats many

days during wintertime.

So there were days where we couldn't come from Denmark to Sweden.

For many, building a transport link to connect Sweden's Malmo and Denmark's

capital, Copenhagen, was just a dream.

It's quite difficult to build because we need to have the road traffic and the

train traffic in the same structure. So it's a very, very big structure we talk

about.

The solution would have to be like no other.

The Orisind Bridge.

The longest cable -stayed rail and road bridge in the world.

At almost five miles long, engineering on this scale required around 157 ,000

tons of steel.

It was seen as one of the biggest engineering challenges.

Engineers came from all over the world in order to see what we had done here.

Despite its size, for civil engineer Niels Lukenberg, the biggest challenge

its location, at one of the world's busiest shipping lanes.

Due to the very large number of vessels passing through Ørstund, we had to leave

a stretch of water open for the traffic in order to avoid congestion.

The answer, a colossal centerpiece off the Swedish shoreline.

Construction began in 1995.

Huge sections of the bridge were prefabricated and towed into position.

Out of the water grew a pair of pylons, roughly 660 feet high, built to support

a span almost a third of a mile long for ships to pass beneath.

This bridge is designed for navigation purposes with a clearance height of 55

meters, so even very large ships can pass through.

However, in this almost 10 -mile -wide strait, a shipping passage is also

off the Danish coast. But here, a bridge is out of the question.

There is a special problem because we have the Copenhagen Airport, which is

quite a big airport, so close to the strait here. We could not build a bridge

the Danish side simply because the high pylons, they would conflict with the

runways.

Remarkably. Instead of going over, they decided to go under.

This is a bridge that morphs into a tunnel.

We are just on top of the entrance to the tunnel.

The tunnel itself is constructed by prefabricated tunnel elements.

which are 40 meters wide and 60 to 80 meters long, floated to this location

and submerged into the trench.

We ended up with a four kilometer long tunnel.

That had never been done in that scale before.

It is the biggest immersed tunnel ever constructed in the world.

Digging the trench with this record -breaking tunnel produces over 264

cubic feet of material from the seabed, used to create the Orison's third

astonishing landmark.

A two -and -a -half -mile man -made island in the middle of the Baltic Sea.

This was a...

Opened in 2000, this hybrid link has transformed the region, connecting two

countries.

Before it took more than one hour just to pass the water.

Now it can be done in seven, eight minutes.

While 20 ,000 cars pass over the bridge every single day, 60 % of those crossing

take the train.

And the shipping lanes continue uninterrupted.

Is it a dream job?

Yes, of course it is.

I've been on many projects in my lifetime, but this one will stand out as

the biggest challenges we had and one of the biggest.

successes we've had for this type of link.

For over 150 years, bridges have opened up the world to trains,

allowing them to cross seemingly

impossible divides.

We think about technology, but it's the hardcore bridges.

They're the things that really make everything possible.

Thanks to Inspired Solutions,

engineers continue to create their impossible railroads.

Bridges are among the most important components of railways all around the

world, helping trains reach their destinations by overcoming formidable

obstacles that stand in their way.

It's really, really gratifying to see it work.

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