Why do different trains take different travel times on the same route?

Different trains take different travel times on the same route because each train has a different category, speed limit, and halt pattern. Rajdhani and Shatabdi trains have fewer stops and higher speed limits, so they cover the distance much faster than a Mail or Express train that halts at dozens of small stations. Some trains have longer commercial halts of five to ten minutes at major junctions while others stop for only two minutes. Freight or passenger trains running on the same track may cause slower trains to be held up at signals. The total travel time also depends on whether the train takes a direct main line or a branch line.