The relationship between train and track

Behind the whole phenomenon of railway transport, there is a very 

complex and absolutely essential interplay namely, the interplay between 

trains and rails. this is far from being a simple case of a vehicle moving 

along a route rather, it is a very intricately constructed self-contained 

system in which each part is supremely optimized to complement each 

other part in such a way so as to make rail travel not just efficient but 

possible in the first place