Functional Safety — IEC 61508 / EN 50129 / ISO 26262 Family

What Is Functional Safety?

Functional safety testing ensures that a safety function exhibits the expected safe behavior in hazardous failure situations; It is an evaluation that is verified by criteria such as hardware fault tolerance, diagnostic coverage and error reaction time. Depending on the sector, IEC 61508, EN 50129 or ISO 26262 applies.

Purpose of Functional Safety

The aim is to prove by both analysis and experiment that the safety function meets the assigned integrity level (SIL or ASIL).

Which Products Is Functional Safety Applied To?

Railway signaling and brake control
Industrial safety control systems
Automotive electronic control units
Process safety instrumentation

In Which Sectors Is Functional Safety Used?

DemiryoluElectricalElectronicsCyber Security

Standards Related to Functional Safety

IEC 61508 serisi
EN 50129
EN 50128 / EN 50657
ISO 26262 serisi
IEC 61511
EN 50155electronic equipment in railway vehicles test
EN 50121electromagnetic compatibility in railway applications test
EN 45545fire safety in railway vehicles test
IEC 61373vibration and shock in railway vehicle equipment test

Functional Safety Conditions

integrity level: SIL 1–4 (IEC 61508 / EN 50129) veya ASIL A–D (ISO 26262)
Hardware metrics: Hazardous failure rate, diagnostic coverage, hardware fault tolerance
Fault injection: Safe response verification by injecting defined failure modes into the system
Software: Development process and validation requirements increase with level

Equipment for Functional Safety

Fault injection test scheme
Hardware/software in-the-loop (HIL) testing platform
Analysis software (FMEDA, FTA)
Measurement and timing recording system

Sample Requirements for Functional Safety

The safety function and safe state must be defined
Integrity level must be assigned
Failure mode list and diagnostic mechanisms should be documented
The need for independent evaluation is determined by level

Duration of Functional Safety

Typically 2–6 months depending on coverage and level.

Functional Safety Procedure

1The safety function, safe state and integrity level are defined.
2Failure mode and effects analysis (FMEDA) is conducted.
3Diagnostic coverage and hardware metrics are calculated.
4Fault injection experiments are applied.
5Error reaction time is measured.
6Evidence is collected in the safety situation report.

Functional Safety Acceptance Criteria

Acceptance criteria are the quantitative and qualitative requirements given for the level of integrity assigned in the applied standard.

Evaluation of Results

The integrity level does not belong to a product label, but to a specific safety function and a defined context. The same hardware can provide different levels in a different application. It is essential to read the safety manual for which functions and assumptions the certificate is issued.

Functional Safety Report

Safety function and safe state definition
Assigned integrity level
FMEDA and diagnostic coverage results
Error injection experiments and response times
Assumptions and usage restrictions

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

Machinery Safety, Railway Safety and industry legislation

Demiryolu Testleri — What Does This Testing Field Cover?

The section below describes the field that the Functional Safety test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Railway testing shows that vehicles and components operate safely and reliably in the rail environment. The character of this family comes from the ASSUMPTION OF LONG LIFE: a rail vehicle is designed for a service life exceeding thirty years and its components remain under vibration, temperature cycling and intensive use throughout that period.

Long life also shapes the component supply chain. Spare parts must remain available for thirty years, electronic components going out of production must be replaced, and every substitution must be re-verified. This takes railways out of a "certify once and carry on" logic.

Fire safety is the most tightly regulated part of the field and runs through the EN 45545 series. The logic of the series rests on the LOCATION OF USE and the OPERATION CATEGORY: a metro running in tunnels and an intercity train do not carry the same risk, and seat fabric and cable are not assessed in the same category. Evacuation time is the main factor setting these categories; because evacuation takes longer in an enclosed tunnel, the material requirements become stricter.

For electronic equipment, EN 50155 is the framework standard and carries environmental, electrical and functional requirements together: supply voltage variations, temperature classes, humidity, vibration and shock. On the vibration and shock side the EN 61373 categories are used and these differ by mounting location — a box mounted on the body and a sensor mounted on the bogie do not go through the same profile.

On electromagnetic compatibility the EN 50121 series applies and addresses a problem peculiar to railways: the traction system switches at very high power and can affect both the systems on board and the signalling along the line. The series therefore carries separate parts for the vehicle, lineside installations and signalling.

For safety-related systems a separate body of work applies, and here the evidence is not testing but PROCESS: EN 50126 (RAMS), EN 50128 (software) and EN 50129 (safety-related electronic systems) define the safety life cycle and the safety integrity levels (SIL). Signalling and brake control systems are assessed within this framework.

On the quality side, the sector's own scheme IRIS (ISO/TS 22163) comes into play; major vehicle manufacturers require this certificate from their suppliers.

On the mechanical structure side, the car body and bogie frame have standards of their own: structural verification under static and fatigue loads, weld quality and crashworthiness. These tests are carried out on full-scale rigs and can take months.

Method groups in this field

Fire safety
Classification of materials and components under EN 45545; the requirement set according to operation and design category.
Electronic equipment
EN 50155 environmental and electrical requirements; supply interruptions, temperature classes, humidity and degree of protection.
Vibration and shock
EN 61373 categories; body, bogie and axle-mounted profiles according to mounting location.
Electromagnetic compatibility
The EN 50121 series: separate parts for the vehicle, lineside installations and signalling.
Safety life cycle
EN 50126 RAMS, EN 50128 software and EN 50129 safety-related systems; SIL determination and the safety case.
Structural verification
Static and fatigue loads on the car body and bogie frame, weld quality, crashworthiness.

Commonly confused in this field

EN 45545 requirements vary with the location of use and the operation category; there is no single "railway fire class".
Conformity to EN 50155 does not cover the vibration requirements; EN 61373 is applied in addition.
A civil EMC report is not sufficient for railways; the EN 50121 series defines a different environment and different limits.
For safety-related systems, testing alone is not evidence; safety life cycle records are required.
A component change (even one driven by obsolescence) requires re-verification; in long-life projects this is routine work.
An IRIS certificate is not a product approval; it is a quality system certificate.

Which decisions these results support

Vehicle and component approval, operator acceptance processes
Material selection according to the fire safety category
The safety case and SIL evidence for safety-related systems
Supply chain quality certification
Continuity of component supply and change management

Related Tests

Frequently Asked Questions About Functional Safety

Will a SIL certified component automatically SIL my system?

No. The integrity level belongs to the safety function. The system level is not proven unless the assumptions and usage restrictions in the component's safety manual are met.