Safety Hierarchy in Engineering Design & Accident Prevention

Machinery and equipment pose many safety hazards in the workplace and to the consumer at home. However, the application of safety hazard analysis and the priorities for accident prevention remain largely the same regardless of the safety hazard presented. A variety of safety hierarchies have existed for decades to guide engineering design where safety hazards are concerned and to promote safety and accident prevention. Understanding this process can also assist in post-accident product evaluation.

Safety hierarchies provide guidelines for the design of any type of equipment that presents a potential safety hazard. Any safety hierarchy first requires that a product evaluation be conducted to identify hazards that may be present under reasonably foreseeable use conditions. Common equipment hazards generally include such things as “fall from”, “caught by”, “struck by” and “contact with”. After hazards are identified, the safety hierarchy process can be used to determine the methodology to address and control the noted safety hazards.

A general safety hierarchy consists of the following priorities in descending order:

eliminate the hazard;
use something that doesn’t create the hazard;
guard against the hazard;
warn and train against the hazard;
finally, what, if any, personal protective equipment (PPE) is applicable.

The elimination of a hazard is always preferable, but not always practical. Therefore, other controls are needed, most notably guarding and warning. These three highest levels of a safety hierarchy are engineering controls, as they are part of the design process. However, training and the use of personal protective equipment also have a role to play in accident prevention. Understanding a safety hierarchy and the pros and cons of the engineering and administrative controls available can be useful when investigating a machine or product after an accident has occurred in order to better evaluate the design and safety choices that were made.