Law, guidance, standards and policy

Fatigue management draws on several layers of information — from statute to internal roster rules. Treating them as the same thing causes confusion, weak governance, and unsafe assumptions.

This page explains the difference between law, guidance, standards, policy and model rules in plain English. It is not legal advice and is not a complete compliance guide.

Legislation and statutory duties

Legislation is law made by Parliament (or devolved legislatures). It creates legal duties that organisations and individuals must meet.

Relevant examples for UK fatigue management include:

The Health and Safety at Work etc. Act 1974, section 2 — general duties on employers to ensure, so far as is reasonably practicable, the health and safety of employees and others affected by their work
The Management of Health and Safety at Work Regulations 1999, regulation 3 — duty to carry out a suitable and sufficient risk assessment

Legislation sets general duties. It does not usually prescribe detailed roster rules for every sector. How duties apply depends on the activity, the foreseeable risks, and what is reasonably practicable in context.

Regulator guidance

Regulator guidance is published by bodies such as HSE or ORR to help dutyholders understand how to meet their duties. It is not statute, though courts may consider whether guidance was followed when assessing whether duties were met.

Examples:

HSE fatigue topic guidance — fatigue as a hazard; risk assessment may include tools such as a fatigue risk index
Managing shift work (HSG256) — HSE guidance on assessing and managing shift work risks
ORR Managing rail staff fatigue — rail industry guidance on fatigue risk management

Guidance can be influential and practical, but it should not be quoted as if it were law. HSE research reports such as RR446 are research, not mandatory thresholds.

Industry standards

Industry standards are often developed by sector bodies or infrastructure owners for use within a particular industry or supply chain. They may be contractually required for organisations working under those arrangements — but they are not automatically UK law for all employers.

An example is the Network Rail standard NR/L2/OHS/003 (Fatigue Management), available through the Network Rail Standards Portal. Organisations subject to Network Rail contracts may need to meet its requirements. That does not mean NR standards are universal UK law, and this site does not reproduce standard text or numeric thresholds.

Contractual requirements

Contracts between clients, principal contractors, and suppliers can impose fatigue-related requirements beyond general law — for example specific roster review processes, reporting, or standards compliance on a project.

Contractual requirements apply to parties to that contract. They should not be presented as applying to all UK workers.

Organisational policies

Organisational policies are rules an employer sets for its own operation — for example maximum shift length, minimum rest between duties, overtime approval, or fatigue reporting routes.

Policies should be proportionate, documented, and reviewed. They may be stricter than minimum legal requirements but cannot lawfully reduce statutory protections.

Model thresholds and software rule sets

Model outputs — such as a Fatigue Index or Risk Index from HSE RR446-based methods — are modelled estimates of relative exposure. They are decision-support, not law.

Many organisations apply colour bands or trigger levels to model outputs. These are organisational policy thresholds that may vary — configured to context and reviewed by competent persons. They are not universal legal limits, and HSE does not currently specify mandatory FI values.

Software may also enforce rule sets (for example flagging gaps between duties). These reflect how the tool is configured — not statute.

Why these layers should not be confused

Layer	What it is	Common mistake
Law	Statutory duties	Assuming law sets detailed roster numbers for every job
Guidance	Practical help from regulators	Treating guidance as mandatory in every detail
Industry standard	Sector/contractual requirements	Presenting a rail or infrastructure standard as universal UK law
Contract	Agreed obligations between parties	Assuming contract terms apply outside that arrangement
Policy	Internal employer rules	Treating internal FI/RI bands as legal limits
Model output	Modelled estimate	Treating a score as proof of safety or fitness for duty

Confusing these layers can lead to weak fatigue risk assessment, misplaced confidence in model scores, or failure to meet actual legal and contractual duties.

Practical implications

Check which duties and requirements apply to your organisation — general law, sector guidance, contracts, and internal policy may all be relevant
Use guidance and models to support assessment and improvement — not as substitutes for competent review
Document who reviewed what, and on what basis — see fatigue records and audit and management accountability
Place tools such as the fatigue risk index within a wider fatigue risk management system (FRMS)

References

Health and Safety at Work etc. Act 1974, section 2 — general duties of employers
Management of Health and Safety at Work Regulations 1999, regulation 3 — risk assessment duty
Fatigue — HSE — fatigue as a workplace hazard
Managing shift work (HSG256) — shift work risk assessment guidance
Managing rail staff fatigue — ORR — rail industry fatigue guidance
Network Rail Standards Portal — industry standards (contractual context; not reproduced on this site)