Signals are provided bearing in mind the following main considerations
- Safety is ensured by the indications offered by the signals
- Operational needs are satisfied
The need to ensure safety is always the topmost consideration and under no circumstances the signalling arrangement can compromise with this primary requirement.
The operational needs is next to be satisfied. thus if a signal is provided which never shows a proceed aspect while safety is ensured nothing is achieved as no train can move on the signal. Hence the need to ensure that the signaling arrangement ensures that trains can be moved effectively.
Satisfying these two considerations require the definition of various types of signals and the location of these signals to result in the best signaling arrangement for a particular use.
Any Signaling arrangement requires to follow a set of rules which are normally ensured by the Railway for ensuring that the trains can be moved safely and in a manner which is desired for the optimization of the use of the facilities.