SIL
Safety Integrity Level
A classification used to define the required level of risk reduction and safety integrity for safety-related systems and functions.
Detailed explanation
Safety Integrity Level (SIL) is used in railway safety engineering to specify the required integrity of a safety-related function. SIL levels range from SIL 1 to SIL 4, with SIL 4 representing the highest safety integrity requirement.
In railway applications, SIL is particularly important for safety-critical signalling and train-control functions where a failure could result in hazardous train movements.
SIL requirements are established through safety and risk analysis and influence the design, development, verification, validation and ongoing management of the relevant system or function.
Railway applications may include:
Interlocking functions
Automatic Train Protection (ATP)
Train detection
Movement authority-related functions
Level-crossing protection
Certain CBTC and ETCS safety functions
For railway signalling applications, the concept is closely associated with the EN 50126 / EN 50128 / EN 50129 railway RAMS and safety framework.
Railway applications
mainline, high_speed, metro, light_rail, freight
Standards and references
EN 50126-1 / EN 50126-2 — Railway Applications – Specification and Demonstration of Reliability, Availability, Maintainability and Safety (RAMS)
EN 50128 — Railway Applications – Communication, Signalling and Processing Systems – Software for Railway Control and Protection Systems
EN 50129 — Railway Applications – Communication, Signalling and Processing Systems – Safety-Related Electronic Systems for Signalling
IEC 61508 — Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems
IEC 62278 — Railway Applications – RAMS
IEC 62425 — Railway Applications – Safety-Related Electronic Systems for Signalling
IEC 62279 — Railway Applications – Software for Railway Control and Protection Systems