Other trains overtake TN when TN is running late and they are running on time. But TN overtakes other trains when
1. TN is running on time and other train is late(Goa, GT, Gondwana, 12447 & many more)
2. TN is running late and other train running late(AP, KK, Charminar, Narayandari etc)
3. TN running ahead of time and other train running on...
more... time.(Mewar, Narayanadri)
4. TN running little late and other train running on time/ahead of time(12171, Shan-E-Bhopal, Pushpak)
Other than this TN has most number of scheduled overtakes for a SF train. Thanks.