Video showing how railway tunnels are cleaned is not what anybody expected

Have you ever stopped to think about how the inside of train tunnels are cleaned?

OK, the thought might not exactly have crossed your mind - it's admittedly pretty dark when your train whizzes through one, and you could be forgiven for assuming the pitch black means the tunnel itself is a sooty, dirty mess.

But a recent viral Reddit post has revealed that yes, train tunnels do get cleaned - and the process itself is pretty mind-blowing.

Redditor North_2006 posted a video on the subreddit Damnthatsinteresting (which can always be relied upon for fun facts) along with the caption: 'Today I learned how railway tunnels are cleaned.' Check it out here:

The fascinating footage shows a train kitted out with multiple shoots of water, pumping outwards and moving in different directions.

This means that when the train enters the tunnel, it's spraying multiple jets of water in all different directions, essentially blasting away any dirt or debris inside.

It's a simple but effective way to keep the inside of a tunnel clean - and a whole lot simpler and less dangerous than sending crews of people inside and doing it by hand.

With more than 39k votes on Reddit so far, it's obviously struck a chord with people - and the top commenter couldn't help but make a joke: "I need a miniature version of this for my colon," they quipped.

While some Redditors don't understand why you'd even bother cleaning the inside of a train tunnel, one commenter made a valid point: "Depends on the fuel being used. Like with chimneys, that buildup can get flammable."

And another helpful explanation read: "Contaminates break down the concrete" - making cleaning necessary.

North_2006/Reddit

It's hard to tell where this video was filmed, although lettering at the bottom of suggests it could be China - but some people are convinced it definitely doesn't happen where they live.

"Subway tunnels in NYC have never seen such a machine," one person deadpanned.

But it looks like this kind of technology is used all over the world, as trains equipped with pressurized hoses which spray water 360-degrees seems to be the easiest way to get the job done.

Take Chinese railway company Railteco, which manufactures train carriages and equipment globally, including a tunnel cleaning vehicle that works very much as we've described.

And as well as water sprinklers for the walls, the specialized train is also 'equipped with eight ground vacuum suction heads, which can automatically clean the ground dirt', the company says.

So there you have it - the next time your train whizzes through a tunnel, you'll know exactly how it gets cleaned.