American Dream

July 27/August 3, 2005

Traffic model maps congestion
By Kimberly Patch, Technology Research News

Quotes:

What do slime mold, airline traffic, fungi, cancer tumors, and computer networks have in common? They all transport something -- nutrients, planes, or information -- from one place to another.

Although there are many examples of systems that solve the classic problem of getting from point A to point B, the extent to which decentralized, or perimeter routes, versus centralized,
or hub-like routes benefit the complicated networks of the real world remains an open question.

Researchers from Oxford University in England have tackled the problem by examining the congestion costs within a network model
that combines paths that go around the perimeter of the network and central hubs that provide shorter paths through the network. Real-world networks are too complicated to describe exactly mathematically. The researchers' model is simple enough to solve exactly, yet realistic enough to provide insights into real networks.

The research is aimed at finding ways to ease bottlenecks in networks involving manufacturing, the Internet and traffic, and
ways to disrupt networks like tumor blood flow and terrorist supply chains. The findings could also help design better networks.

"This general scenario of passing packets -- cars, data, food, information, documents -- between two points occurs in a wide range of systems, said Neil Johnson, Professor of Physics at Oxford University. These include roads, air traffic, the Internet and communications networks, fungi, crime networks, cancer tumors, large organizations, and supply chains, he said.

In each case, the same interplay between centralized and decentralized pathways and control arises. "Going through the
center has the advantage of shorter distance but has a higher risk of congestion and hence longer overall journey-time," said Johnson. "Going around the center has a lower risk of congestion but a larger geographical distance," he said.