Name: Why Are There Stones Along Railway Tracks?
Uploaded: 2026-01-17T13:43:22.000Z
Duration: 5 min 41 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Next time you're waiting at a train station or watching a locomotive thunder past a crossing, look down.

Beneath those massive steel rails and heavy wooden ties,

Rough, gray, jagged stones stretching out for thousands of miles.

It doesn't matter if you're in India, the UK or the United States.

Why do we rest our most advanced high speed trains on a loose pile of rocks?

Why don't we just bolt the tracks to a solid concrete road?

The answer isn't just about saving money.

It's a brilliant piece of engineering that protects the train from sinking into the earth.

And it hides a surprising history that connects modern railways to ancient sailing ships.

Welcome to Simple Things: Surprising Histories.

Today, we're uncovering the secret of the railway stones.

To understand the stones, we first have to understand the problem.

We are talking about millions of pounds of steel and cargo.

If you placed that much weight directly onto the ground,

the intense pressure would crush the soil.

The tracks would sink, buckle, and the eventual train would derail.

This is where the stones, technically known as track ballast, come in.

They sit on those horizontal beams which we call sleepers or ties, and

The job of the ballast is to act as a cushion.

It takes the immense concentrated weight of the train and spreads it out over a wide area.

It dissipates the pressure so the ground underneath doesn't get crushed.

The tracks are not actually fixed to the ground.

If you look closely, you'll see the tracks are floating on the stones.

They aren't bolted into the earth deep below.

They rely on friction and the sheer weight of the ballast to stay in place.

This flexibility allows the track to slightly absorb the vibration of a roaring train,

Now, you might be thinking, "Okay, stones support the weight.

If you were to pick up a piece of track ballast, you'd notice something immediately.

You will never see smooth, round river pebbles on a railway track.

And there is a very specific engineering reason for that.

Imagine stepping into a pit of ball bearings or smooth marbles.

If a train went over smooth, round rocks,

the stones would roll away under the vibration and the track would slide apart.

Engineers used crushed stone--usually granites or quartzite--that has been smashed into sharp, angular shapes.

When these jagged stones are packed together, they don't roll.

creating a solid, immovable mass that still allows for a little bit of flexibility.

They lock the track in place, preventing it from sliding side to side.

Even when a high-speed train screams around a curve,

the stones don't just hold the weight; they fight the two biggest enemies of the railway.

If we laid tracks on a solid concrete slab or just bare dirt,

Dirt turns to mud, which washes away, leaving the track unsupported.

Concrete creates puddles which can rust the steel rails.

But a pile of stones is perfectly porous.

When it rains, the water flows instantly through the gaps in the stones and away from the track,

You rarely see a jungle growing in the middle of a train track.

That's because this thick layer of sharp rocks makes it incredibly difficult for plants to take root.

If plants were allowed to grow, their roots would break up the soil and ruin that stable foundation we need.

So the stones act as a weight bearer, a drainage system, and a weed killer all in one.

Before we finish, here's one last surprising detail.

Centuries ago, when empty wooden ships sailed to pick up cargo,

They would bob around in the waves to weigh them down.

Sailors would fill the ship's hold with heavy stones.

When the ships arrived at port to load up their goods,

they would dump these stones on the shore.

Early railway engineers looking for cheap heavy material to stabilize their new tracks looked at these piles of discarded ship stones and thought, "Perfect."

They used the ship's ballast for the train tracks and the name stuck.

So the next time you see those jagged gray stones, you'll know they aren't just rocks.

They're a self-draining, weed-fighting, weight-bearing,

engineering marvel that has kept the world moving for 200 years.

This is Simple Things: Surprising Histories.

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