Let’s go underground shall we? Now, you know that feeling when you’re so excited
that your bladder suddenly goes too full? If you’re here in the subway, it might prove
tricky, because there are generally no bathrooms around. Why’s that? Or how, for that matter,
can you even breathe so deep underground? There are so many questions about the subway
waiting to be answered, so off we go!
How come streets and buildings don’t collapse underground above the subway?
You’d think a huge hollow space right beneath your feet would cave in sooner or later, but
somehow it doesn’t. That’s because subway tunnels use supports that don’t allow the
soil above them crumble. The supports are usually made of concrete and completed with
metal bracers for additional safety. By the way, there’s an impressive digging machine
that not only bores the tunnel but also constructs concrete supports on the go.
Why is it warm in the subway in winter and cool in summer?
You might guess a great climate control system, but that wouldn’t be it. On most subway
stations, there’s no climate control at all. The comfy temperature depends entirely
on the laws of physics. Cooler air tends to go down, so when it’s summer, all the heat
inside a station goes up, while down below it’s much more pleasant. In winter, the
heat from all the electrical appliances makes the stations warm, and there’s also no wind
inside, so it doesn’t feel as cold as outside.
Why do you feel a gust of wind when opening the door of a subway station?
If the station is of a closed type, you open the door and feel the blow of warm air from
inside. This happens because of a difference in pressure: within the station it’s higher
than in the street to better get rid of fumes. So when you open the door, the air escapes
with force.
Why is there a third rail in the subway? Commuter and high-speed trains all have two
rails they ride on, but in the subway, you may notice a third one either between the
two main rails or on the side of the platform. No, underground train cars don’t have an
extra set of wheels. The third rail is there to provide electric power to the train. The
main rails aren’t electrified, so nothing will happen to you if you touch them. This
also increases the chances of survival if someone falls onto the tracks. The third rail,
though, conducts a lot of electricity, so you’d best avoid it to prevent becoming
a small fry. And on that note…
Why doesn’t subway use overhead power cables? Like I just said, there’s a third rail to
convey power to a subway train. Commuter trains, on the other hand, have overhead power lines
that support them. The trouble is that such lines use a very high voltage, which isn’t
safe for underground trains — the power lines would just be too close. So the subway
started using lower voltage and higher current power sources, which needed a thicker conductor.
And so begins the story of the third rail. Another reason for not having the lines up
above in the subway is that there are no people who would need to walk or drive over the power
supply. This makes the subway quite a safe place to be.
Why are subway maps so geographically inaccurate? You must’ve noticed that subway maps always
show stations equally spaced from each other, and the lines on them are almost perfectly
straight. In reality, though, tunnels make turns pretty often, and the distance between
stations differs a lot. Maps are drawn this way because underground it doesn’t really
matter where exactly you are. The really important thing is the ease of reading because passengers
need only to understand which station they need to get off the train. The credit in design
of the modern maps goes to Harry Beck who invented the London Tube map back in 1933.
Why is it so windy in the subway? Apart from the powerful ventilation system,
there’s another driving force that makes the air move fast: trains. When a train arrives
to the station, it pushes the air in front of it, creating strong gusts of wind. And
since trains come and go pretty often, the air doesn’t really stop moving at all. So
better not stand too close to the edge of a platform — you might end up blown over!
How come you can breathe so deep underground? Some subway stations are quite shallow and
you only need to take a few steps down to catch a train. But there are also deep ones,
where you have to take an escalator to get down to the bottom. For such stations, air
shafts are constructed outside the main station building. They provide fresh air down below,
which is great, because otherwise the air in the station would really deplete quite
soon. Also when the air gets pumped into the station, it goes through a serious filtering
system, so you get REALLY, REALLY fresh air.
Why is there cellular reception in the subway? When you’re traveling so deep underground,
surrounded by metal and concrete, it would seem no signal could pass through these walls.
But more often than not you can use your phone and even post things on the Internet while
sitting in the middle of a tunnel. This is thanks to the small antennas installed within
the tunnels. The drawback is that Internet connection might be slow because an antenna
connects to a cell tower at a certain bandwidth, and the more people use it on the same station,
the less speed each user gets.
Why are there no public bathrooms on subway stations?
It might come off as a surprise, but there are plenty of public bathrooms on subway stations
across the world. Still, not all of them are equipped with these facilities, and some only
have staff bathrooms. Subway workers can let passengers use those, but they can also refuse
to do so without any explanation. Anyway, there are two main reasons why there
are no public bathrooms: safety and financing. They’re ridiculously expensive to maintain,
so I guess we won’t be seeing many of such cabins where they weren’t before. And the
second reason is of a security concern, since there can be no cameras installed in the bathroom,
and any kind of suspicious activity would go unnoticed.
Why do escalator handrails move faster than the stairs?
Having to constantly pulling your hand back on the handrail might be annoying, but there’s
a reason it leaves the stairs behind. In fact, they’re supposed to move at the same speed,
but handrails wear down faster than the stairs, so they are set to a more energetic pace from
the start. With time, they slow down, and the stairs gain on them.
Why are there mostly no guardrails on subway platforms?
In the US, like in many other countries, nothing separates passengers from the drop on the
subway tracks. This might seem dangerous, especially since many people do fall on the
tracks, but the problem is that a human operator can’t control the train so precisely as
to fit the doors to the gaps in guardrails. Maybe later, when all trains are completely
automated, some sort of passenger protection will appear.
How are subway trains coordinated to avoid accidents?
It’s amazing how underground trains have this small interval of just a couple of minutes
between them, and yet manage not to bump into each other every so often. For this to work,
they’re coordinated from the central computer. The tracks are divided into short sections,
or blocks, and when a train is on a block, it sends a signal to the central computer
that it’s occupied. If there’s another train closing in from another direction, the
safety equipment will warn the operator, and the second train will stop to let the first
one pass. And if the operator can’t stop the train themselves for some reason, the
automatic braking system will trigger and force it to halt.
How do train operators stop at the exact spot they ought to? Because they’re really really
good at it. Well that too. A subway train is a long vehicle with many
cars, so it seems surprising that it should always stop exactly where it should. But that
isn’t some kind of magic — professionals say it’s just practice and markers. There’s
always a big and obvious marker on the wall of the tunnel that tells the operator to start
braking, and if they do it correctly, they slow down and crawl to the right spot. It
isn’t exactly the same all the time, either, it’s just really close to perfect so nobody
sees any difference. So what’s your takeaway here? Try to be
a small fry, only once, when you’re a tot. Two times, not so good.
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