Safety in Numbers? Peter Jacobsen talks about bicycle and pedestrian safety.


creative commons licensed ( BY ) flickr photo shared by D Coetzee

Last Friday transportation consultant Peter Jacobsen was the featured speaker of the ITS Berkeley Transportation Seminar. He discussed his reseasrch in bicycle and pedestrian safety captured in his seminal paper, "Safety in Numbers" (Injury Prevention, v.9 no. 3, 2013). One of the questions he raised was how to define safety. Is it reflected in the data (number of incidents) or behavior (which is difficult to tease from that data)? Jacobsen remarked that, "No one swims in shark infested waters." So when people think it is safer to ride their bicycle or walk, they will be more likely to do so - this is the crux of the safety in numbers thesis. Jacobsen's anaylsis showed that if cycling and walking increase by 300%, the individual's risk only increases 50%. This is also why Jacobsen's anlysis shows that cyclists in Upland, CA have 8-times greater risk than cyclists here in Berkeley. He then suggested there needs to be more research into whether or not more bicycles increase safety for pedestrians and vice versa. 

Jacobsen also made an interesting observation that increased pedestrian safety is not tied to behvaior. He related an anecdote about pedestrians in Sacramento who are very alert because they don't expect cars to yield to them, while pedestrians in Berkeley are often more distracted (with their heads in their phones) because they know cars will yield. Their comfort with the situation is reflected in their behavior. Jacobsen also used the iconic crosswalk of Abbey Road as an example of the evolution of street markings for safety. Watch the live stream now to see it in action - flashing crossing lights, zig-zag lane markers, and more to make it safe for crossing. 

He also discussed other papers that had interestesting observations about bicycle/pedestrian safety. One, "For heaven’s sake follow the rules: pedestrians’ behavior in an ultra-orthodox and a non-orthodox city," by Rosenbloom, Nemrodov, and Barkan compares pedestrian compares pedestrian behavior in an ultra-orthodox Israeli city to that in a quite secular city. The other is "Evidence on Why Bike-Friendly Cities Are Safer for All Road Users" by Marshall and Garrick, which investigates if bicycles improve traffic safety for all modes.