Here's the Physics Behind That Insane Chinese Traffic Jam
A few days ago, a drone captured this eye-popping video of the world’s worst traffic jam on the G4 Beijing-Hong Kong-Macau Expressway. Blame foggy weather if you like, but physics says it all comes down to a question of density — namely, an unusually high number of people returning to Beijing after a week-long holiday festival.
I’ve never seen anything like this, and I live in Los Angeles; the City of Angels frequently tops the list of places with the worst traffic in the US, along with Washington, DC, San Francisco, New York City, Atlanta, Chicago, and even Seattle. Traffic flow is a big problem in most major urban centres. The average US motorist spends 36 hours every year in traffic delays. But China — man, China takes the crown when it comes to insanely congested traffic. A study last year found that the average Chinese driver spends the equivalent of nine days a year stuck in traffic.
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When this happens — when all the cars are travelling at close to the same average speed because of the vehicle density on the roadway they become highly dependent on one another. A physicist might compare the relationship to the correlated motion of electrons in metals, which gives rise to weird phenomena like superconductivity.
Highly correlated traffic means that a tiny perturbation — a butterfly flapping its wings, or a single driver braking unexpectedly — will send little ripples of corresponding slowdowns through the entire chain of cars behind him/her. That’s one reason why slowdowns and traffic jams occur most commonly at merge points, especially exit and entrance ramps, or when lanes are closed due to road construction.
http://www.gizmodo.co.uk/2015/10/heres-the-physics-behind-that-insane-chinese-traffic-jam/
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