November 15, 2019


Safety in Numbers for pedestrians and bicyclists: Implications for public policy


1:40pm - 3:00pm


1605 Tilia, Room 1103, West Village


That motorists are a lot less likely to hit someone walking or bicycling if more people walk or bicycle surprised researchers. In contrast, the number of car crashes increases proportionally with the number of cars. The evidence of a prevalence effect implies that injury risk is more than just a matter of physics, and that something occurs with human physiology or psychology. Safety in Numbers likely occurs because humans have difficulty detecting rare items. That injury risk decreases with more walking and biking creates opportunity for implementing public policies for reducing damage to the climate and improving health. This non-linear risk also explains why the recent NTSB recommendation for compulsory bicycle helmet laws could increase injury risk.

Biographical Sketch

Peter Jacobsen is a professional engineer with a strong interest in the health impacts of transportation policy. His published work ranges from injury prevention to activity promotion. His published article in ITE Journal explains to traffic engineers why the physiology of young children prevents them from coping with the dangers of traffic and why engineers need to adapt residential streets to the needs of children. His influential study, Safety in Numbers, showed that the risk of a motorist hitting a pedestrian or a bicyclist decreases as more people walk or bicycle, and hence the health goals of injury prevention and activity promotion can work together to improve health. A subsequent study showed that this lower risk is likely due to human limitations in detecting rare objects. He is currently bringing state-of-the-art roadway engineering to improve health by encouraging physical activity and reducing severe injuries.

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