In this respect, it can be said that all the train rakes running on the are I Rlys tracks including the premier ones like Rajdhani/ Shatabdi/ Duronto etc are under utilised !! The culprit here is the slack time given to the trains so as to accommodate large number of passenger/freight trains jostling for "green Signal" to move along in the limited Indian railway Network, and to facilitate the regular track maintenance activities.
If all trains get green signal through out their run about 20-35% of the running times can be saved for most of the express trains on IRly network.
Mumbai...
more...

Rajdhani enjoy topmost priority (minimum slack time, interesting to compare with NZM-TVC Raj) where as the Talgo train, I guess should have got through green signal for NDLS-BCY journey (w/o any provision of slack time)
Talgo was expected to do NDLS-BCTin 13 hrs against 16 hrs of Raj i.e. a gain of 3 hours For same priority, technically only time Talgo train can save is faster acceleration/ deceleration at stops and speed restrictions due to very small train load (about half hour?) and higher speed maintained on curves (say another half - to one hour). Rest of the time it was supposed to gain i.e. 1.5-2 hrs should be due to difference in slack time.
One burning example in this respect is, HWH-CSTM Duronto, which had same operational speed (105/110kmph) as other super-fast trains like Gnaneshwari/ Geetanjali but much higher avg. speed of 75kmph against just 55-60 kmph for the other S/F trains on the route. On the inaugural run (yr 2009) the Duronto (the pet train of RM) was given through green signal and the avg. running speed between 2 stops (excluding stoppage time) was around 90-95 kmph, where as the same for other S/F trains was 60-80 kmph, indicating how the slack time given to trains drastically increase the journey times.