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. Hey, if you learned something new today, then
give the video a like and share it with a friend! And here are some other videos I think
you’ll enjoy. Just click to the left or right, and stay on the Bright Side of life!