Metro Rail

This list of metro systems includes electrified rapid transit train systems worldwide. In some parts of the world, metro systems are referred to as subwaysU Bahnen or undergrounds. As of December 2017, 178 cities in 56 countries around the world host the approximately 180 metro systems that are listed here. The London Underground first opened as an “underground railway” in 1863 and its first electrified underground line opened in 1890, making it the world’s oldest metro system. The metro system with the longest route length is the Shanghai Metro; the busiest one is the Beijing Subway; and the one with the most stations is the New York City Subway.

The locations of all the world’s metro systems.


The metro rails actually work on the principle of DC shunt motors …no usage of gears …many parts are electrified so do not poke the loose connections they can ash you in 1 in 10th sec.

The METRO consists of microcontroller with the RF receiver and the voice recorder chip with speaker .The whole system is attached to the vehicle (Train). When the project is powered the train moves, until it encounters a RF card placed beneath the track. The encoded RF transmitters are placed in the railway stations.

The microcontroller in the TRAIN is programmed in such a way that every station name saved in the voice chip which is having a unique code. So whenever the bus or train reaches the station, the receiver in the train receives the codes, which are transmitted form the transmitter and the microcontroller receives this code and checks in the look up table, saved in the chip. Which ever matches, the controller will send the command to the voice chip to play that particular voice, the announcement can be done for 6 seconds with the station number and the place. At the same time the train stops for about 10 seconds in the station and then before leaving the station, it will again start to announce “THE TRAIN IS LEAVING” and the train starts to move to next station.

The voice chip will play the voice and this will be heard in the speaker. This voice is repeated till the train leaves the station. In this module LCD is used for the
display purpose, in the programming what we have stored it will be displayed in the LCD. For E.g.: station number will be displayed when the train reaches the station, even when the train is leaving it will display on the LCD even it will announce it using the IC chip, the train is in which station and when it is leaving also. Buzzer is used in this module; it will give beep sound when the train reaches a station and when it is leaving station every time.

Vacuum Brake system

Signalling and communications

The trains use centralised automatic train control (CATC) comprising automatic train operation (ATO), automatic train protection (ATP) and automatic train signalling (ATS) systems.

Intercoms are provided for emergency communication between the passengers and the driver in each coach, and on-train announcements are in Hindi and English. There are also route maps and LCD display systems in every coach.

Fare collection is through contactless, stored-value smartcards. The metro has its own police force.

What is ATO?

Automatic train operation (ATO) is an operational safety enhancement device used to help automate operations of trains. This is achieved according to the Grade of Automation (GoA) present, up to GoA 4 level, where the train is automatically controlled without the presence of staff on board. Mainly, it is used on automated guideway transits and rapid transit systems which are easier to ensure safety of humans. Most systems elect to maintain a driver (train operator) to mitigate risks associated with failures or emergencies.

Many modern systems are linked with Automatic Train Control (ATC) and in many cases Automatic Train Protection (ATP) where normal signaller operations such as route setting and train regulation are carried out by the system.

The ATO and ATC/ATP systems will work together to maintain a train within a defined tolerance of its timetable. The combined system will marginally adjust operating parameters such as the ratio of power to coast when moving and station dwell time, in order to bring a train back to the timetable slot defined for it.

What is ATP?

Automatic train protection (ATP) is a type of train protection system which continually checks that the speed of a train is compatible with the permitted speed allowed by signalling, including automatic stop at certain signal aspects.

If it is not, ATP activates an emergency brake to stop the train. ATP systems are now a legacy, defunct technology that has been superseded throughout Europe and internationally by the European Rail Traffic Management System.

What is ATS?

Automatic train stop or ATS is a system on a train that automatically stops a train if certain situations occur (unresponsive train operator, earthquake, disconnected rail, train running over a stop signal, etc.) to prevent accidents.

In some scenarios it functions as a type of dead man’s switch. Automatic train stop differs from the concept of Automatic Train Control in that ATS usually does not feature an onboard speed control mechanism.

What is CBTC?

Communications-based train control (CBTC) is a railway signalingsystem that makes use of the telecommunications between the train and track equipment for the traffic management and infrastructure control. By means of the CBTC systems, the exact position of a train is known more accurately than with the traditional signaling systems. This results in a more efficient and safe way to manage the railway traffic. Metros (and other railway systems) are able to improve headways while maintaining or even improving safety.

A CBTC system is a “continuous, automatic train control system utilizing high-resolution train location determination, independent from track circuits; continuous, high-capacity, bidirectional train-to-wayside data communications; and trainborne and wayside processors capable of implementing automatic train protection (ATP) functions, as well as optional automatic train operation (ATO) and automatic train supervision (ATS) functions,” as defined in the IEEE 1474 standard.

What is PTC?

Positive train control (PTC) is a system of functional requirements for monitoring and controlling train movements and is a type of train protection system. The term stems from control engineering. The train is only allowed to move in case of positive movement allowance. It generally improves the safety of railway traffic.

Train protection systems are used to control traffic movement by technical means. They are especially needed in cases of high speed transportation, dense traffic with short succession of trains and mixed type traffic at widely differing speeds. Train protection systems were in practical testing at least since the beginning of the 1930s in Europe. Stopping a running train is the main goal of any train protection system. This is most easily done with stop order, and without a special order the vehicle is allowed to run. A typical representative for this “negative train control” is Indusi. In contrast to this ‘easy moving’, a PTC restricts the train movement to an explicit allowance; movement is halted upon invalidation.

The main concept of PTC (as defined for North American Class I freight railroads) is that the train receives information about its location and where it is allowed to safely travel, also known as movement authorities. Equipment on board the train then enforces this, preventing unsafe movement. PTC systems may work in either dark territory or signaled territory, and may use GPS navigation to track train movements. Various other benefits are sometimes associated with PTC such as increased fuel efficiency or locomotive diagnostics; these are benefits that can be achieved by having a wireless data system to transmit the information, whether it be for PTC or other applications.

The Federal Railroad Administration (FRA) has listed among its goals, “To deploy the Nationwide Differential Global Positioning System (NDGPS) as a nationwide, uniform, and continuous positioning system, suitable for train control.” The U.S. freight rail industry had said that at the end of 2018, the nation’s largest freight railroads were operating PTC across 83.2 percent of the required route miles.  The American Railway Engineering and Maintenance-of-Way Association (AREMA) describes Positive Train Control as having these primary characteristics:

  • Train separation or collision avoidance
  • Line speed enforcement
  • Temporary speed restrictions
  • Rail worker wayside safety

Basic operation

A typical PTC system involves two basic components:

  • Speed display and control unit on the locomotive
  • A method to dynamically inform the speed control unit of changing track or signal conditions.

Optionally, three additional components may exist:

  • An on-board navigation system and track profile database to enforce fixed speed limits
  • A bi-directional data link to inform signaling equipment of the train’s presence
  • Centralized systems to directly issue movement authorities to trains

PTC infrastructure

There are two main PTC implementation methods currently being developed. The first makes use of fixed signaling infrastructure such as coded track circuits and wireless transponders to communicate with the onboard speed control unit. The other makes use of wireless data radios spread out along the line to transmit the dynamic information. The wireless implementation also allows for the train to transmit its location to the signaling system which could enable the use of moving or “virtual” blocks. The wireless implementation is generally cheaper in terms of equipment costs, but is considered to be much less reliable than using “harder” communications channels. For example, the wireless ITCS system on Amtrak’s Michigan Line was still not functioning reliably in 2007 after 13 years of development, while the fixed ACSES system has been in daily service on the Northeast Corridor since 2002 (see Amtrak, below).

The fixed infrastructure method is proving popular on high-density passenger lines where pulse code cab signaling has already been installed. In some cases, the lack of a reliance on wireless communications is being touted as a benefit. The wireless method has proven most successful on low density, unsignaled dark territory normally controlled via track warrants, where speeds are already low and interruptions in the wireless connection to the train do not tend to compromise safety or train operations.

Some systems, like Amtrak’s ACSES, operate with a hybrid technology that uses wireless links to update temporary speed restrictions or pass certain signals, with neither of these systems being critical for train operations.

Locomotive speed control unit

The equipment on board the locomotive must continually calculate the trains’ current speed relative to a speed target some distance away governed by a braking curve. If the train risks not being able to slow to the speed target given the braking curve, the brakes are automatically applied and the train is immediately slowed. The speed targets are updated by information regarding fixed and dynamic speed limits determined by the track profile and signaling system.

Most current PTC implementations also use the speed control unit to store a database of track profiles attached to some sort of navigation system. The unit keeps track of the train’s position along the rail line and automatically enforces any speed restrictions as well as the maximum authorized speed. Temporary speed restrictions can be updated before the train departs its terminal or via wireless data links. The track data can also be used to calculate braking curves based on the grade profile. The navigation system can use fixed track beacons or differential GPS stations combined with wheel rotation to accurately determine the train’s location on the line within a few feet.

Centralized control

While some PTC systems interface directly with the existing signal system, others may maintain a set of vital computer systems at a central location that can keep track of trains and issue movement authorities to them directly via a wireless data network. This is often considered to be a form of Communications Based Train Control and is not a necessary part of PTC.

Trackside device interface

The train may be able to detect the status of (and sometimes control) wayside devices, for example switch positions. This information is sent to the control center to further define the train’s safe movements. Text messages and alarm conditions may also be automatically and manually exchanged between the train and the control center. Another capability would allow the employee-in-charge (EIC) to give trains permission to pass through their work zones via a wireless device instead of verbal communications.

Technical limitations

Even where safety systems such as cab signaling have been present for many decades, the freight railroad industry has been reluctant to fit speed control devices because the often heavy-handed nature of such devices can have an adverse effect on otherwise safe train operation. The advanced processor-based speed control algorithms found in PTC systems claim to be able to properly regulate the speed of freight trains over 5,000 feet (1,500 m) in length and weighing over 10,000 short tons (9,100 t), but concerns remain about taking the final decision out of the hands of skilled railroad engineers. Improper use of the air brake can lead to a train running away, derailment or to an unexpected separation.

Furthermore, an overly conservative PTC system runs the risk of slowing trains below the level at which they had previously been safely operated by human engineers. Railway speeds are calculated with a safety factor such that slight excesses in speed will not result in an accident. If a PTC system applies its own safety margin, then the end result will be an inefficient double safety factor. Moreover, a PTC system might be unable to account for variations in weather conditions or train handling, and might have to assume a worst-case scenario, further decreasing performance, In its 2009 regulatory filing, the FRA stated that PTC was in fact likely to decrease the capacity of freight railroads on many main lines. The European LOCOPROL/LOCOLOC project had shown that EGNOS-enhanced satellite navigation alone was unable to meet the SIL4 safety integrity required for train signaling.

From a purely technical standpoint, PTC will not prevent certain low-speed collisions caused by permissive block operation, accidents caused by trains “shoving” in reverse, derailments caused by track or train defect, grade crossing collisions, or collisions with previously derailed trains. Where PTC is installed in the absence of track circuit blocks, it will not detect broken rails, flooded tracks, or dangerous debris fouling the line.