Haddon’s paper, On the Escape of Tigers, describes an orderly way to design-out the risks of accidents. Even at 50, it’s a great example of Lewin’s point that there is nothing so practical as good theory. Haddon powerfully applies Gibson’s insight that transfers of energy are what hurt people (or damage assets) in accidents. Haddon presents his scheme as a ranked list of ten strategies. At the top is “prevent the marshalling of the form of energy in the first place”. At the bottom is “all the measures…” needed to heal or repair. The scheme’s been adapted many times (e.g. in MORT). NRI recently adapted it to help frontline construction workers find, in other people’s accidents, safety lessons for their companies. That approach is about taking a fresh look at familiar conditions. The Haddon scheme seems to help. The scheme is literal, and makes the physics accessible. In contrast, talking about ‘barriers’ as metaphors (e.g. training) creates a fog in which administrative actions seem equivalent to physical interventions. Instead, by starting with physics, we think first about what’s ideal, and then pass those prevention ideas through a filter of what’s practical. ERIC PD is the better known cousin of the Haddon scheme. Both contain the idea that, when planning or designing anything, one exhausts the most effective strategy before moving to the next best. Rather than ‘energy transfers’, ERIC uses ‘hazards’— a sometimes slippery concept. But try both; which is best most likely depends on the users and their context.