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Transportation networks are among the most important building blocks in the economic development of a country. The structure and performance of transportation networks reflects the ease of travelling and transferring goods among different parts of a country, thus affecting trade and other aspects of the economy. In the recent years, complex network analysis has been used to study several transportation networks. These include airport networks (for instance, the airport network of China [1], airport network of India [2] and the world-wide airport network [3, 4]), urban road networks [5, 6] and railway networks [7, 8, 9, 10, 11]. Some commonalities have been observed in the topological properties of almost all transportation networks, such as small-world properties. On the other hand, certain topological properties, such as the cumulative degree distribution, have been found to differ widely—power-laws for Indian airport network [2] and world-wide airport networks [4], two-regime power-laws for the China airport network [1] and US airport network [12] as opposed to the exponential degree distributions of the railway networks of India [10] and China [9].

It is to be noted that several different models have been used in literature to study transportation networks, and the observed topological properties often depend on the way the network is modelled. Most studies, including the ones referred to above, adopt a common network model where two nodes (airports or stations) are linked by an (undirected) edge if there exists a direct connection (flight or train) between the two nodes 1. On the other hand, a directed network model was used in [11] to study the …