Attenuation and Fall Protection Performance

https://www.change.org/good_practice_working_at_height_update_Steve_Tilling

Working at Height Good Practice Advocacy

Ask the GPG to add a section explaining the primary performance trade-offs when using different forms of fall protection. Once you understand this, the real value of higher-level controls becomes apparent, and you can compare different control schemes.

Fall protection has a hierarchy of just three principles once you understand the simple mechanics of a fall from height. You can calculate these, but they're also easy to understand conceptually.

See my fall forces article if you are interested in the numbers behind falling.

The Dangerous Consequences of Falling

The primary hazard we are controlling for is a type of energy called gravitational potential energy. Anything elevated accumulates this energy, and the farther you can fall, the greater the potential energy; the more mass the thing or person has, the greater the potential energy.

The key risks of this hazard are the triggers and interactions that release this energy and convert it to kinetic energy: the fall event.

Edges are the obvious ones, but penetrations, fragile surfaces, unstable ladders, and more are risks that arise from this singular potential energy hazard. Elevation creates the hazard, and the only elimination is to not be elevated, to eliminate the potential energy.

The guidance should focus on the specific risks and how they are managed, but contextualised with this understanding, and the fall hierarchy that applies to the controls.

The issue is that releasing that energy causes acceleration, and like your car, the longer you accelerate, the longer it takes to stop safely. This is attenuation, and like your car, you can use the brakes and trade energy over distance as an averaged force, or you can crash and release that energy as a peak force. An arrested fall is a compromise with a delicate balance, easily disrupted by poor decisions.

—The fall protection hierarchy always starts with avoiding the trigger or interaction, and this requires being able to identify the triggers and interactions.

—Next is managing input force by reducing fall potential (height). A fall as small as 600mm can create about 6kN of force to remove (~600kg) and happens in 1/3 second. A 2m fall can create 20kN of force (2000kg) in 2/3 second, and it only gets worse as the fall potential increases.

—Lastly, you can manage the attenuation of the fall by mitigating the peak forces through deceleration distance, or conformal pressure distribution, ideally both. This is about managing the output after the trigger. Controls in this regime are not preventative; they are managed consequences.

These three protection principles are always applied, and protection systems and techniques just target different regimes for different contexts. You can remember them with the acronym A.R.M: Avoid, Reduce, Mitigate. But even in this simple model, there is overlap because they target different elements.

• Avoidance targets worker agency -  from being aware - to physical prevention.
• Reduction works whether you are avoiding or mitigating, as it represents potential risk
• Mitigation targets worker error, and the methods depend on the reduction regime.

If you would like to see these principles in guidance, let me be your voice and sign the petition to show support so I can advocate on your behalf.

https://www.change.org/good_practice_working_at_height_update_Steve_Tilling