The Emergence of Small-World Phenomenon in Urban Transportation Networks: An Exploratory Analysis

Abstract

‘Small-world networks’ is a new concept that is receiving a lot of attention. Introduced by Watts andStrogatz (1998), a ‘small-world network’ is based on ‘six degrees of separation’, or the notion that everyone in the world is related to everyone else through at most six acquaintances. ‘Six degrees of separation’ arises from the existence of cliques and a few popular individuals who provide connections between these cliques. Small-world networks are similar in that they have a high degree of local clustering or cliqueness, like a regular lattice and a relatively short average minimum path, like a completely random network. Unlike the idea of six degrees of separation though, they do not assume random connectivity. Instead, they lie somewhere in between a regular lattice and a random network. Watts and Strogatz (1998) assert that this phenomenon is probably universal, applying to many natural and manmade networks. The United States power grid, the neural network of a particular type of worm, and the social network of acting coworkers are three networks for which this is demonstrated.