It is impossible to imagine the urban rhythm of life without underground highways that carry millions of passengers every day. Subway train is a complex engineering complex that combines the achievements of mechanics, electrical engineering and automation. For the average person, this is just a means of transportation from point A to point B, but for engineers it is a living system that requires constant monitoring and accurate calculations.
Unlike surface railway transport, the metro operates in a confined space, which dictates special requirements for safety and energy efficiency. Subway cars designed to withstand enormous loads during frequent acceleration and braking. Understanding how this type of transport works helps us understand the scale of the infrastructure hidden under our feet.
In this article, we'll take a closer look at the anatomy of underground trains, look at the evolution of traction systems, and learn what technologies allow trains to run at 90-second intervals. You'll find out why metro car can't just go off the tracks and how the collision avoidance system works.
Design features of a subway car
The basis of any rolling stock is the body, which is a supporting structure. Modern subway cars are made of stainless steel or aluminum alloys, which can significantly reduce the weight of the structure without loss of strength. This is critical for saving energy when accelerating a heavy train.
Each carriage rests on two bogies, which are the key element of the chassis. It is the bogies that ensure smooth running at rail joints and dampen vibrations transmitted from the track. Inside the carts there are wheelsets, which have a special ridge geometry that allows them to reliably stay on a narrow track and navigate sharp turns in tunnels.
- 🚇 Trolley frame - the main load-bearing element connecting the wheelsets and the body.
- 🔋 Traction motor - a device that converts electrical energy into mechanical rotation of wheels.
- 🛑 Brake system — a set of mechanisms, including disc and magnetic rail brakes.
It is important to note that the interior of the carriage is also subject to strict fire safety and ergonomics standards. The seats are often made of non-flammable materials, and the doors are equipped with an anti-pinch system. Unlike long-distance trains, the metro does not have vestibules between cars in the classical sense, which ensures end-to-end passage throughout the entire train.
⚠️ Attention: Passengers are strictly prohibited from opening doors manually or delaying their closure. The door mechanism has enormous compression force, and interfering with its operation can lead to injury or disruption to the schedule of the entire section of the line.
Traction and power supply systems
The heart of any electric train is the traction system. Historically, subways use 825 volt direct current, although there are also alternating current systems around the world. Energy is supplied through contact rail, located on the side of the running tracks, or through the overhead contact network (in the case of a metro tram).
Modern trains such as the series Moscow 2020 or Innovia Metro, equipped with asynchronous traction motors. They have a number of advantages over old-type commutator motors: smaller dimensions, lack of sparking and the possibility of energy recovery. When braking, the engine switches to generator mode, returning part of the electricity to the network.
Traction control is carried out through a pulse-phase control system or, in newer models, through water-cooled inverters. This allows you to smoothly regulate the speed without jerking, which is especially important when stopping frequently. Converters take current from the contact network and convert it into current of the required frequency and voltage for the motors.
What is energy recovery?
Regeneration is the process of converting the kinetic energy of a moving train into electrical energy during braking. Instead of burning the energy in braking resistors (converting it into heat), the train "gives" it back to the catenary system, where it can be used by other trains on the same section or by station lighting systems. This allows you to save up to 30% energy.
Types of metro trains: from “E” to “Moscow”
The history of the development of the metro is reflected in the types of rolling stock. In Soviet times, the main types were cars E, D and F. They were characterized by simplicity of design, but lacked modern comfort. The series of cars became a transitional stage 81-717/714 (“Numbered”), which can still be found in many cities of the post-Soviet space.
The modern standard is wide-format through-aisle trains such as the 81-760/761 "Oka" or "Moscow". Their main feature is the absence of partitions between the driver’s cabin and the passenger compartment, as well as between the cars themselves. This creates the effect of a single space, improves air circulation and increases safety, since the driver can see what is happening in the first car.
There is also a division by size:
- 📏 Dimension "A" — wider and higher cars (used in St. Petersburg, Nizhny Novgorod, Kazan).
- 📏 Dimension "B" - standard Moscow sizes, most common in Russia.
- 📏 Light metro — reduced trains for lines with lower passenger traffic.
The choice of train type depends on the year the tunnels were built and the diameter of the shield with which they were laid. You cannot simply launch a wide car “A” into a tunnel built for gauge “B”, since it simply will not fit in width or height. Infrastructure and rolling stock must strictly correspond to each other.
Pay attention to the car type marking on the end part. This will help you understand what kind of train you are driving and find out its technical characteristics in open sources.
Automation and traffic safety systems
The movement of trains in the metro is regulated by sophisticated automation systems. The fundamental principle is the block system, which divides the path into block sections. There can only be one train per section. Traffic lights and speed are controlled by the system ALS-ARS (automatic locomotive signaling with automatic speed control).
If the driver exceeds the speed limit or tries to drive through a prohibiting signal, the system will apply emergency braking without human intervention. In modern systems such as CBTC (Communication-Based Train Control), intervals between trains are calculated in real time with high accuracy, which allows you to reduce waiting times to a minimum.
| System | Operating principle | Advantage |
|---|---|---|
| ALS-ARS | Speed control via track circuits | High reliability and reliability |
| CBTC | Data transmission via radio channel | Minimum intervals |
| ARS (Automotive driving) | Full train control by computer | Elimination of the human factor |
A special place is occupied by the system for preventing passengers from falling on the tracks. On new lines they are installed platform sliding doors, which open synchronously with the train doors. This completely eliminates the possibility of a person accidentally or intentionally falling under an arriving train.
⚠️ Attention: Being behind the limit line on the platform when the train arrives is deadly. The aerodynamic flow created by a passing train can pull a person under the cars even without physical contact.
The role of the driver in train management
Despite the high degree of automation, the role of humans remains key. Subway driver is not just an operator pressing buttons, but a specialist responsible for the lives of thousands of people. His task is to monitor the operation of systems, monitor the boarding and disembarkation of passengers, and act in emergency situations.
The driver's workplace is equipped with many instruments and screens. The cabin is sealed and protected from tunnel noise. Responsibilities include checking the technical condition of the train before leaving the depot, adhering to the schedule to the second and constantly monitoring the signaling.
Training to become a driver takes a long time and includes studying the structure of all train components, technical operating rules and the psychology of behavior in emergency situations. Profession requires excellent health, resistance to stress and quick reaction.
☑️ Qualities of an ideal metro driver
Maintenance and life in the depot
At night, when the metro is closed to passengers, a different life begins for the trains. The trains are sent to depots - special complexes for repair and storage. It is held here maintenance (MOT), which can be daily or periodic, depending on the mileage.
In the depot workshops, specialists check the condition of wheelsets, brake systems, pantographs and doors. Special equipment is used for turning wheels, diagnosing electrical circuits and checking the tightness of pneumatic systems. Any, even the slightest malfunction, must be eliminated before the next entry onto the line.
There is also the concept of a major overhaul, which is carried out every few years. During this process, the car is almost completely disassembled, the interior is updated, electrical equipment is replaced, and the body undergoes troubleshooting. After such repair metro car gets a second life and can serve for decades more.
Without daily night service at the depot, safe operation of the metro is impossible. It is the work of repairmen, hidden from the eyes of passengers, that guarantees the reliability of the system.
Frequently asked questions (FAQ)
Why do metro trains sometimes stop in the tunnel between stations?
This can happen for several reasons: waiting for the block area ahead to be cleared, a temporary power outage in the contact network, or the activation of security systems. Dispatchers are doing everything possible to restore traffic.
What is the maximum speed a subway train can travel at?
The design speed of most modern metro cars is about 90 km/h. However, on stretches the speed is limited by the track profile, the curvature of the tunnel and the traffic schedule, so the average commercial speed usually does not exceed 40-50 km/h.
What to do if you forgot something in a subway car?
You must immediately contact the station duty officer or the lost & found service. If the train has not yet left, the attendant will contact the driver or dispatcher. If the train has left, the search for the item will be carried out at the end of the line or in the depot.
Is it true that there is no cellular service in the metro due to the thickness of the walls?
This used to be the case, but now most lines have special antennas and signal amplifiers installed. However, in deep tunnels the signal may be unstable due to the shielding effect of metal and concrete, as well as interference from the train.