Vivek Express: ऊंचे नीचे रास्ते और मंज़िल तेरी दूर.

@others on this post.
Except for NDLS-AGC, where speed limit is imposed at 150 KMPH (MPS), on other sectors, the normal MPS will be 80/100 KMPH, depending upon the train.
On the side of the coaches (where they are coupled together) you will see the maximum speed marked for that coach.
Engineering Restrictions, for repair of tracks, replacing or other kinds of work...
more...

to make the rail line stable would induce a restricted speed which would be marked on the side from where it commences, in the form of a triangle showing a figure (say 50) and at the terminating point a circular board marked (T/P) meaning restriction terminated for passenger trains and boards which say (T/G for goods trains.
Entering into loop lines and passing through main lines on buzy stations would require the LP to slow down while negotiting the crossing which is normally 30 or 40 or even lower depending upon the number of loops the train has to negotiate. this applies even when the train is going through the station. This reduces the AVERAGE speed of the train. Where there is a halt at the station, in addition to the time allocated for the halt, the same procedure would have to be followed
To reduce speed from 100 or 80 to say 30/40 means that the LP starts slowing down the train much in advance so as to avoid pulling brakes sharply causing jerks to passengers and also endangering the train itself.
Thus the average speed is affected by it. To compensate for this loss of time, most trains have 'extra' slack time built into its running time. This is NOT visible in any published, PUBLIC time table.
Good wishes.
Murli/mAS