Freight trains are very slow movers and huge drag on the speed of faster express trains they have great inertia and take a very long time to pick up speed and clear a section of track. Heavier axle load cause much wear and tear of tracks making them unfit for higher speeds . Elimination of these will substantially increase the avg speed of all the express trains in general.
Automatic signaling is also gradually being taken up by IR, I hope at least NDLS-UMB section shall be done soon.