The Life-Sized City Blog

Robert Doisneau - running pedestrians in Paris We recently covered the disturbing and archaeic 85th percentile method and how it is applied for (and by) vehicles. If you thought THAT was fun, you might also enjoy The 15th Percentile. It is frequently used to determine the time between the WALK and DON'T WALK crossing signals -  in other words, how much time the engineers computer models allow for human beings to cross streets. It's not as rooted as a standard as The 85th Percentile, but it is still widespread. In a nutshell, we should be paying more attention to pedestrian crossings, when you consider statistics that say that " 40% of accidents involving pedestrians occur at these intersections ". In Europe, one in four pedestrians die on a crossing . What seems to be the problem? In the U.S., the Manual on Uniform Traffic Control Devices (MUTCD) establishes a “normal” pedestrian speed at 1.2 metres per second (m/s), so traffic signal times are set according...

It's not like we needed any more proof that we live in car-centric cities. When you start scratching just a little below the surface, however, you start to discover that we are not so much citizens in cities but rather a flock of reluctant characters in The Matrix. You discover that we live in cities that are controlled by bizarre and often outdated mathematical theories, models and engineering “solutions” that continue to be used despite the fact that they are of little use to modern cities. One of them is called The 85th Percentile. It's a method that cities all over the planet use to determine speed limits. It's the standard. Nobody questions it. Certainly not the engineers and planners who, for decades, have been served it up and who have swallowed it whole during their studies. Which reminds us of the old traffic engineer joke: Why did the engineer cross the road? Because that's what they did last year. The concept is rather simple: the speed limit of ...