Thank you so much sir, I understood why the IR and IRI values can differ from each other. But kindly tell me one thing. Why these two values 1652 kms and 1701 kms (IRI source) are differing from each other, for the up and down train? I am quite sure that the train follows exactly the same path for up and down journey. (If you want to be too much accurate, the little bit difference because of curvature and whatever cannot be more than 1 km). Even I can see that for 12443, it is still being shown in its route map that it passes via Asansol, Dhanbad etc. Is that really so for this train? Please have a look.