Chapter 1 

1.What is ERTMS ?
The European Railway Traffic Management System (ERTMS) is a major Train Control development to enhance cross-border interoperability through Europe by creating a single standard for railway signalling.
More than 20 different national signalling and speed control systems exist in the European rail system, with each one incompatible with the other. It creates an obstacle to the free flow of rail traffic across Europe.
Imagine the difficulty in operating a train with different signalling rules ,signals , even with two different systems you turn off one onboard computer and turn on another and change driver with route knowledge each time you cross the border!

Thalys high-speed train, which connects Paris, Brussels, Cologne and Amsterdam, is equipped with a minimum of seven different systems for its cross-border operation. 
The ongoing deployment of a single common system, such as the ERTMS, aims at removing this technical barrier to cross-border passenger and freight movement.

The ERTMS also saves maintenance costs, improves safety and increases traffic capacity. 
It reduces the headway between trains and allows for a maximum speed up to 500km/h. It increases the current capacity by up to 40% without the need for any infrastructure upgrades.
The project is being implemented by eight UNIFE (the Association of the European Rail Industry)  and the GSM-R (Global System for Mobile Communications – Railway) industry. 
The UNIFE members include Alstom Transport, Ansaldo STS, AZD Praha, Bombardier Transportation, Invensys Rail, Mermec, Siemens Mobility, and Thales.

In nutshell The European Rail Traffic Management System defined a  standard for safety, signaling and communication. Throughout Europe, ERTMS is getting  implemented on all high speed lines, specific transit corridors and eventually on all railways. 
ERTMS as a definition consists of all aspects considering management, safety and communication in the whole railway system. Subsets of ERTMS are ETCS, which stands for European Train Control System and GSM-R, a radio communication system.
Note:GSMR is getting obsolete and Long Term Evolution (LTE),otherwise known as 4G/5G  is considered as the alternate communication medium.ETCS includes all systems necessary for both drivers’ cab and track signaling. 
In some publications ETML (European Track Management Layer) and INESS (Interlocking Safety System) are also counted to belong to ERTMS?

2. ERTMS Principles 
ERTMS’ concept is based on standardization of data exchange in traffic management. This can best be compared with the operational methods in aviation. Aircraft can always land on every international airport due to  exchange of standard data then the use of standard systems and procedures for takeoff and landing. Like in aviation, trains should be able to connect stations, regardless the country they are in, crossing over having their destination. 
This principle however does not implicate automatically that all trains have exactly the same systems on board. Airplanes don’t have that either by the way. They only things really standardized in aviation are communication procedures and specifications of communication equipment. Communication in this perspective means both communication between the train and equipment alongside the track, as well as between train and traffic control centre. Differences between certain interfaces showing information to the driver are still possible.

Track – Train communication 
Thi is where ETCS comes in. ETCS states specifications for track – train communication, consisting of several systems: 
• Eurobalise: standardized beacon, acting as an interface between track and train; 
Note : Balise is the French word for Beacon /Transponder.
• Eurocab: standardized cab equipment for the use of ETCS, replenished with specific transmission modules (STM), facilitating existing network specific safety systems. 
• Euroradio: GSM-R is gsm for railways. GSM-R is used for communication, data exchange and – on longer term – positioning; 
• Euroloop: facility of loops, making rail guided data exchange possible. 
Trains equipped with the Eurocab always have STM available, as this interface makes it possible to operate on non-ETCS lines as well, then using the traditional safety system. 
ERTMS can be implemented on new railways as well as on existing lines. To accomplish compatibility three different levels were developed.

 

3.ERTMS Levels 

ERTMS consists of three different Levels 

Note : (Intermediate Levels are not considered  which will be covered in detail ) 

•Level 1 :Continuous Track-Train Communications; 
•Leve 2 :Continuous Train-Radio block centre Communications;
•Level 3 :Moving Block Technology (Almost like CBTC used in urban lines,but some features like Train regulation missing in Level 3 ) 
System upgrades are possible by expanding components, meeting specifications of the next level.

Level 1 
ERTMS level 1 is connected with traditional lines equipped with trackside  signals and detections. Communications are ensured by means of beacons (“balise”) located adjacent to signals alongside the tracks. 
As soon as a movement authority is received trough a beacon, the ETCS on board equipment calculates the permitted speed ,taking the characteristics of the train into account .The Trains speed is under continuous monitoring by the system 
ERTMS level 1 can relatively easy  to make traditional lines interoperable, ensuring automatoic braking when maximum speed is exceeded. 

Level 2
ERTMS level 2 does not require signals along the tracks. Movement authority is therefore not necessarily communicated by a fixed signal, but by means of a radio block centre (RBC) to the on board ETCS unit which is equipped with GSM-R
The inline beacons communicate data like location, limits on speed, gradients on the way etc .The information about data and signal ahead is shown to the driver on a cab display. Level 2 counts with a braking distance factor, to ensure there is an adequate braking path available.
The removal of trackside fixed signals and replacement by beacons can raise the capacity of a line significantly. 

Level 3 
Level 3 allows “moving block technology” to come in. Whilst level 1 and 2 sill operate with fixed sections and thus limiting use of a block to one train 
at the time, level 3 supplies the control centre of continuous information about the train’s position. 
In this level, the train itself is to be regarded as a “moving block” and is a fully radio based system without any trackside equipment. 
The Radio Block Centre (RBC) receives positioning of each train continuously and calculates smallest possible train distances at any time. 
Therefor the track is no longer separated in fixed blocks but split into “moving blocks”. 
At the same time it is vital that trains guarantee their integrity as there is no trackside equipment available to provide this information. ETCS L3 is not yet matured at this time of preparation 

4.ERTMS Technology 
With ERTMS beacons (“balise”) are used for data transfer.
Information transfer 
In level 1 there is communication from track to train only. The beacons transfer information to the trains, containing: 
• the beacon’s identification; 
• distance remaining to next point of speed changing;
• target speed of train (in relation to braking path etc.); 
• validity of the information. 
In level 2 communication is two way: from track to train and reversed. The beacon’s signals are the same as in level 1, but in level 2 the train 
communicates about data too. In fact it sends information to the radio block centre (RBC) by means of GSM-R.
In L-3, which is still in conceptual stage, is based on moving block technology.
 It involves use of special equipment within the train to continuously supply data on the train’s position to the control centre, rather than by track based detection equipment. 
The train thus continuously monitors its own position.

Transition 
When a train moves from a traditional line to ERTMS-covered tracks an entry beacon is used to register with the RBC. Specific information about the train – length, weight, braking path etc) is being sent with the registration.