The hierarchy of control is the framework used to structure risk control measures in order of effectiveness. It is a fundamental principle of health and safety risk management and sits at the core of every well-produced RAMS document.
Why the hierarchy exists
Not all control measures are equally reliable. The hierarchy ranks controls from most to least effective based on how much they depend on human behaviour to work. Controls that remove or change the hazard at source are always more reliable than controls that require operatives to behave in a specific way every time they carry out a task.
The five levels
Elimination is the most effective control. It involves removing the hazard entirely — redesigning the task so the hazardous element does not exist. Eliminating the need to work at height by carrying out the work from ground level, specifying pre-assembled components to avoid cutting on site, or changing the sequence of works to remove a confined space entry requirement are all examples of elimination. Where elimination is reasonably practicable it should always be the first option considered.
Substitution involves replacing a hazardous material or process with a less hazardous alternative. Using a water-based product instead of a solvent-based one, specifying pre-cut materials to reduce manual handling loads, or choosing a less toxic adhesive are substitution controls. Substitution does not eliminate the hazard entirely but reduces its severity at source.
Engineering controls are physical measures that do not rely on human behaviour to work. Edge protection, machine guarding, local exhaust ventilation, vehicle exclusion zones with physical barriers and acoustic enclosures are all engineering controls. Because they work regardless of what any individual operative does, they are inherently more reliable than controls that depend on people following procedures correctly.
Administrative controls include safe systems of work, permit to work systems, supervision requirements, training, inductions and procedural rules. They are less reliable than the controls above them because they depend on people following the procedure correctly every time. They remain necessary and valuable but should supplement engineering controls rather than replace them where engineering controls are reasonably practicable.
PPE sits at the bottom of the hierarchy because it is the only control that must be used correctly by the individual operative on every occasion in order to work. Edge protection protects whether the operative remembers it or not. A harness only protects if it is worn, fitted correctly, and clipped to a rated anchor point. PPE is appropriate as a supplementary control alongside higher-level controls, or as the primary control only where no higher-level control is reasonably practicable.
Applying the hierarchy in practice
When writing control measures for a RAMS document, work through the hierarchy for each significant hazard. Start at the top — can this hazard be eliminated? If not, can it be substituted? If not, what engineering control can be applied? What administrative controls are needed alongside it? What PPE is required as a final layer?
The most common failure is jumping straight to PPE. A manual handling assessment that lists "gloves and back support belt" as the control measure has not considered mechanical aids, task redesign or load reduction. An excavation risk assessment that lists "hard hat and safety boots" has not considered the engineering controls required to prevent collapse.
The hierarchy in RAMS review
When reviewing a submitted RAMS, check each control measure against the hierarchy. If PPE is listed as the primary or only control for a significant hazard, the reviewer should ask why higher-level controls were not applied and whether the document adequately justifies that decision. In most cases the absence of higher-level controls is an oversight rather than a reasoned decision, and the document needs revision.
Applying the hierarchy is one thing; writing it down so a supervisor can enforce it is another — how to write control measures that actually work is the practical half. Work at height has its own statutory version of the same sequence, set out in what a work at height RAMS must include. Controls that stop at PPE are flagged in every review: understanding your report explains how findings are ordered.
This article is general guidance on UK construction documentation practice. It is not legal advice, a compliance certification or a substitute for review by your own qualified health and safety personnel, who remain responsible for deciding whether any particular document is adequate. See our disclaimer.