Tuesday, December 25, 2007

Using math to avoid the Christmas traffic jam

Have you ever been stuck in bumper-to-bumper traffic and then with no apparent reason the traffic just starts moving again at 60 mph? A team of mathematicians from the Universities of Exeter, Bristol and Budapest published the reason why in the journal Proceedings of the Royal Society.

Something as simple as a slow truck moving into a different lane on a busy highway - defined as more than 25 vehicles per mile, or one every 200 feet - can cause a ripple effect called a backward traveling wave.

University of Exeter Dr. Gábor Orosz said, "When you tap your brake, the traffic may come to a full stand-still several miles behind you. It really matters how hard you brake - a slight braking from a driver who has identified a problem early will allow the traffic flow to remain smooth. Heavier braking, usually caused by a driver reacting late to a problem, can affect traffic flow for many miles."

Just great. Now we can ruin hundreds of people's day just by braking too late on the highway.

1 comment:

Graham said...

Interesting. I first characterized traffic as a compression wave (of space between cars) propagating backwards through the line of traffic when I was 17, and came up with the optimal solution: to dampen the wave, allow a large space to form between you and the car in front of you, and do not use the brake at all, if possible, just coast until you have created the pocket. The wave never has a chance. Of course, if some muttonhead then pulls into your lane in front of you and begins accelerating and braking frantically, you have to start again:-)