Betweenness Centrality is a measure for quantifying the probability that a street segment falls on a randomly selected shortest path linking any pair of segments. Mathematically it is effectively the same as the space syntax measure of choice.
Freeman, L. (1977) A set of measures of centrality based on betweenness, Sociometry 40, 35-41. pp. 37;
Hillier, B., Burdett, R., Peponis, J., Penn, A. (1987), Creating Life: Or, Does Architecture Determine Anything? Architecture et Comportement/Architecture and Behaviour , 3 (3) 233 – 250. pp.237
Hillier , B. & Iida, S. (2005), Network and psychological effects in urban movement, In: A.G. Cohn and D.M. Mark (Eds.): COSIT 2005, LNCS 3693, pp. 475-490