The forklift driver was texting. - He didn't see the pedestrian. - The collision caused serious injuries.

Open and shut, right? All the investigators in the room nodded. Write the report. Ban mobile phones, on the shop floor. Add the ban to the induction training. Done.

Then someone ask the question, "Why was the pedestrian there?"

Silence.

The pedestrian was a supervisor. He was taking a shortcut through the warehouse because the walkway added five minutes to his route, between offices. Everyone took the shortcut. They had done for years.

"Why isn't anyone using the designated walkway?"

Because it was designed when the facility was smaller. The offices were relocated three years ago. But the walkway layout stayed the same. Taking the designated route meant walking three sides of the warehouse instead of cutting straight across the work floor.

Why has no one redesigned the walkway? Because the warehouse layout has not been designated as anyone’s responsibility. The operations team assumes the H&S team will flag the warehouse layout. The H&S team assumes the operations team will request changes, to the warehouse layout. Meanwhile everyone adapts.

This is what systematic investigation looks like. Not one "why," but systematic investigation asks layers of whys. A systematic investigation builds on each why to reach the answers.

We started with a distracted driver. We ended up with the organisational structure, the warehouse design and the informal systems people create when the formal systems do not work.

Here is the hard truth: the mobile phone ban may make us feel better. The mobile phone ban will not prevent the next incident. The next incident will still happen because we have not looked at why people are in the danger zone in the first place. We need to ask why people are, in the danger zone.

When I do an investigation I do not look for a single failure. I continue to investigate and peel back the layers until I see the failures that lined up and made the incident inevitable.

Next time: I'll show you the tool I use to map these layers and identify where your defenses actually failed.