You've just made your way out of a really frustrating traffic jam, and you're looking around for the reason, maybe an accident or roadworks, but you can't see anything. So, what in the world just happened?
Mathematicians use different models to explain these so-called phantom traffic jams.
One popular model likens traffic to a flowing liquid and traffic jams to a shockwave.
To investigate this, Japanese researchers put 22 cars on a circular track, and ask them to drive around at a steady 30 kilometers per hour.
For a little while, all goes well, but it takes just one car to slightly change speed to cause problems, making the car behind slow down further, and the next car back to slow down even more again.
The cars begin to clump together, and this clumping effect reverberates backwards around the track like a shockwave, even leaving to brief halts at points.
Theoretically, if traffic remains heavy, this traveling wave could just keep going and going forever.
These invisible waves of congestion also occur in real-life traffic jams.
They create a ripple effect which doesn't go away until all cars return to the same pace.
To prevent a jam, you should maintain a steady speed, so no changing lanes, no slowing down to look at things, and using your cruise control.
And you can always carpool or use public transport to reduce congestion in the first place.
Another potential solution is driverless cars, which are better at keeping a constant pace, and which can wirelessly communicate with each other to respond to changing traffic conditions.
Mathematicians help, too, by improving the algorithms that control our traffic lights, and predicting when and where traffic jams will occur.
And now, four fast facts about pesky traffic:
Traffic light timings optimize movement for the majority of traffic,
meaning that if you're driving against the flow, you could hit a frustrating run of red lights.
Traffic psychology studies show that women cyclists are given more space on the road than men, and you're more likely to let a car in front of you if you have passengers.
Using theoretical physics to understand traffic congestion is creatively called "jamology."
And in 2010, a 100-kilometer stretch of highway between Beijing and Tibet came to a standstill for two weeks, possibly the greatest traffic jam in history.
Stuck for ideas about traffic jams?
Check out our website where we have some links, and we'll see you around back here next week.
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