After one (stampede) in 2006, Saudi authorities instituted single-direction pathways, visitor counts, and theme park-like scheduling of visits. The Jamarat Bridge, location of three pillars that represent the devil, at which pilgrims are supposed to throw stones, was the site of a stampede that killed over 1,000 people; today it’s a multi-level, multi-exit complex designed to keep people moving. In the past decade or so, the Saudi government has worked with a wide variety of architects and designers, including the famed international firm Gensler, to improve flow and safety at all of the hajj’s major sites, from the central mosque to the tent city.
Put that many people in so confined a space, though, and preventing stampedes will always be a challenge. Part of the problem is fluid dynamics—except people are the fluid.
According to Helbing’s (a computational social scientist who studies crowd dynamics at ETH Zurich) model, pedestrians are essentially just trying to avoid obstacles—including other pedestrians—while making their way to a given destination as quickly as possible. At low densities, which is to say no crowds, you get laminar flow, as smooth as a flat-bottomed, fast moving river.
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