SPEEDING traffic can suddenly become a traffic jam鈥攋ust like gas
becoming a liquid, say German physicists.
Boris Kerner of Daimler-Benz in Stuttgart and his colleague measured the
speed and density of traffic on a three-lane motorway. As the rush hour started
and the density of traffic increased, the average speed just past a feeder road
suddenly dropped at two critical points.
The first drop came when it started to become difficult to change lanes, and
the second when a jam occurred. The data showed close parallels with phase
transitions in which gases turn into liquids, the scientists say.
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鈥淚 think the work is very useful,鈥� adds Kai Nagel of Los Alamos National
Laboratory in New Mexico. 鈥淚t could help us to design road networks so that
these breakdowns don鈥檛 happen.鈥� The findings will appear in next week鈥檚
Physical Review Letters (vol 79, p 4030).