Comment by mjlee
One boss (ship's captain for context, but I think this applies more widely) would call careless slip-ups "lemons", as in one armed bandits. One lemon was fine, happens from time to time. Two was a cause for concern. Three and everything stops to evaluate what's going on and for people to reset.
Knowing about the swiss cheese model is great, but you also need to have some heuristic about when those holes might line up and bite you. Typically it's when people are rushed, stressed and tired and you have to be able to spot that even when you're rushed, stressed and tired.
That said, forgetting to put on your hi-vis might be a careless error, but walking outside of marked pedestrian zones and operating a forklift while using a phone absolutely aren't! The forklift driver fleeing the scene makes me think safety culture had to be abysmal.