1. A method of designing a transport network for routing a plurality of routable flows, said transport network having a plurality of network elements and a plurality of connections between said network elements, the method comprising: a) defining a first network configuration and at least one alternative network configuration for said transport network; b) calculating for each of said first and any alternative network configuration, a probability function representing, for each maximum number of routable flows, the probability of routing such a number of flows in the network configuration currently considered, wherein said probability function is calculated as the ratio between the number of times that a maximum number of routable flows has been successfully routed by means of a test routine repeated a predetermined number of times, and the number of times said test routine has been repeated; c) calculating for each of said first and any alternative network configuration, a complexity function calculated as the ratio between a sum of complexity factors relative to the network elements of the network configuration currently considered and said probability function; and d) comparing the complexity functions of said first and any alternative network configurations, for choosing a network configuration having a lowest complexity value.