It is not strange to find more than one Chilango who has a love hate relationship with the city subway. Well, sometimes it works fast and well, but sometimes nothing else does not give one. However, few stop to think that the subway also needs to take its time (literally) and that sometimes, only sometimes, there is a reason why its operation is not ideal outside of the obvious failures. As well, In this note we tell you how the Metro Collective Transportation System works (or how it should work).
Types of wagons
First of all you should know that There are two types of subway lines: railway and pneumatic. Differentiating them is very simple: the first one you can recognize because the cars have a kind of antenna on the top that is connected to cables installed on the tracks. Meanwhile, the second type does not have this antenna. You can also differentiate them because one uses metal wheels and the other uses air. Guess the name that corresponds to each one. As you probably know, only metro lines A and B belong to the railroad group, while the rest use pneumatic cars.
Let’s say more about this. I think I always wanted to know what exactly the “antenna” of the railroad cars was for, and now that I find out, I think the answer was not so difficult to guess. It is called pantograph and serves to carry electric current to the cars. They are also connected to a wiring consisting of 7 bolts from which a power cable hangs.
As for pneumatic wagons, there is not so much mystery. They are called that because they use inflated tires (pneuma means air or spirit in ancient Greek), and they have a kind of disc behind each tire that serves as a spare in case the main tire is struck.
How the tracks work
If you have stopped to observe the tracks, you may have noticed that there are three main axes on each side of the track: two on the sides and one in the middle that is higher than the sides. Well, each of them has a name and a function. The one in the middle is called the “guide bar” and is responsible for carrying the electric current to the cars. It carries an approximate 750 V, which is equivalent to almost seven times the power our homes receive under normal conditions. So, if you ever fell on the tracks you should avoid touching or even approaching the guide bar at all costs.
The sidebar that is on the side that the users ascend to the wagons is called the “raceway” And, as the name suggests, it is the base on which the tires roll. It has no other function and does not carry electric current. And it is attached to the other axis, which actually looks like a small notch made in this bar.
This third axis is called “safety rail” as it serves as a replacement for the raceway in case the main tire is punctured.. As we said before, the wagons or pneumatic lines use rubber tires, and behind this tire a metal spare is installed, which comes into contact with the safety rail in case that one is deflated.
Types of driving
There are two main types of ways a subway train can be driven: manually and automatically. In both cases there must be a driver monitoring the controls.
The autopilot is the default and the most common in the stations we regularly travel. The autopilot regulates the speed of the train’s progress, as well as the moment at which it must stop. In this mode the driver only has control over some functions of the cars, such as the closing of the doors, the control of the audio, lights, etc.
Manual driving has three subtypes, and is usually used in special cases such as when there is a breakdown. The first of these is the so-called controlled manual driving mode, and is used in secondary operations such as changing roads, changing trains, etc. In this mode, the driver has control over some operations such as the following: train speed, indicate the moment in which he should move forward and the moment of braking. However, some safety functions are still activated, so it could be said that there is no absolute control over the train. For example, you cannot advance more than five meters in reverse, and you cannot pass a red light, because when you try it, a brake is automatically activated.
The third type is also manual and is called “limited manual driving.” The driver’s attributions are basically the same as those of the previous type, although it can be reversed more than five meters. This mode is only used in operations at terminal stations and in service centers when a train needs a revision or something like that.
The last type, predictably, is the one that gives full control to the train operator. It is then able to choose the speed of the train, the moment of starting and braking, etc. It also means that automatic security systems are disabled. It is only used on special occasions as a very serious breakdown at some station.
Automatic piloting of the trains of all the subway stations in the city would not be possible without a control center to monitor their progress. It is located in the center of Mexico City and regulates the traffic of the 12 subway lines in real time.
There is an operator for each line that has in front of him a board clearly out of the 1970s with red lights, some numbers and other information that represents the progress of the trains. He has several tasks under his charge, among which are to inform drivers about the conditions of the line, the speed of the trains, and can even monitor the activity of the stations through surveillance cameras. He is also in charge of cutting the energy that feeds the wagons in case it is required to perform any operation directly on the tracks.