Priceonomics

You probably love sitting in traffic for no apparent reason. Oh you don’t? Well lets investigate the culprit of most traffic jams - people that brake too hard. You do that sometimes too? Oh, well then you're part of the problem.

Sure, sometimes traffic jams are inevitable: road maintenance, bottlenecks, and accidents can grind traffic to a halt. But what about when it’s bumper-to-bumper for no apparent reason? Journalist Andrew Marr spoke with motorway specialist Eddie Wilson to find out. According to a computer simulation developed by Wilson, the “phantom traffic jam” has a cause. The heavy foot. Wilson explains the cause of phantom traffic jams in this short video:

All it takes is one driver hitting his or her brakes too hard to slow everything down. That braking sets off a ripple where cars behind it also need to break until at the end of the chain reaction, traffic has come to a stand still. Even when cars start moving at the front of this chain reaction, the tail end of cars halted in traffic keeps growing.

In the simulation model, the cars at the front of the traffic jam are already moving while the cars at the rear are still braking and adding to the queue of standstill traffic.

So if an impatient driver behind you is getting dangerously close, know that his bad karma could possibly be starting a traffic jam a mile behind when he hits the brakes. That’s probably of no comfort to anyone actually.

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