EMC on the face of it may not be specifically safety-related, but it certainly forms the important part of safety regulations for all the railway systems. Under the EMC directive, there are a series of standards that are applicable to the railway systems only. While EN 50121 is the main standard laid for the railways, there are subgroups of this standard that cater to various aspects of the railways’ operation.
In any railway system, it is essential that the traffic moves smoothly, and safely. The railway signaling system is essentially a program to ensure this. The need for such a system was felt to avoid the collision of the trains at any point in the route, while many trains operate on a particular route.
Starting from the early days the rail signaling was known as Block signaling, which meant blocking of the train on a certain route to let the other train pass. .For this purpose the railway lines are divided into blocks so that only one train can pass through the block at a particular time, However, later on, fixed signals were erected on the poles located near the tracks to indicate the movement of trains. These signals were still in use have different colors to indicate the advice to the train driver for proceeding, stopping or waiting for some time. Further, mechanical signals were installed which reduces the work for most of the gang men on the rail route.
The modern railway signaling system will require computerized operations, while having the proper synchronization of software and hardware to ensure the safety of the railway system, as per the standards laid out. .The required signaling system has to be quite robust and above all, it must have the electromagnetic compatibility with the other apparatus and equipment working in the rail system as such, whether onboard or along the route.
The signaling system must be immune to the surrounding electronic or electrical devices operating within the railway system so that it does not cause any harm or impair the functionality of these devices in any manner. .  .