How many trains, on average, should it take to get from any arbitrarily chosen railway station in India to another? A group of young researchers from Kolkata tried to find this out. Their results: a majority of stations in India are either connected by a single train or require a single change of train to connect them. A small fraction is connected through 2 changes, a still smaller fraction requires three changes of trains and surprisingly 4 changes of train to connect any two stations in the network is almost negligible.

This remarkable fact suggests that the Indian railway network is a