Way back in about 1985, it was observed that there was only one fully electrified trunk route i.e HWH-Dhanbad-NDL in IRlys and all other electrified sections (mainly on Trunk Lines connecting 4 metros) were in small stretches of a few 100 kms. It was realized that the benefits of electrification were not being reaped by IRlys due to frequent changes of locomotive from electric to diesel and vice versa for long distance trains were leading to losses in following way:
(1) Operational problems like frequent change of crew and poorer productivity of loco pilot crew as well as poor productivity of electric locomotive to large extent and of diesel locomotive to some extent. A lot of manpower was being wasted in loco...
more...

coupling and decoupling operations.
(2) Trains were getting slowed down due to lot of time (typically 15 minutes) wasted in loco changing.
(3) Lot of diesel and electric power was being wasted in loco movements during change of traction.
(4) Loco movements were eating up line capacity at stations and were causing delay in entrance of stations at traction changeover stations.
Then it was decided in the national interest that all the trunk routes which were carrying very heavy freight as well as passenger traffic and very much qualified for electrification be fully electrified so that the same loco can take the train from one corner of the country to other.Accordingly following routes were prioritized for quick electrification:
(1) Delhi-Mumbai via Ratlam (MTJ-BRC) as well as via Itarsi (IT-Bhusawal)
(2) Delhi-Chennai (MTJ-BZA)
(3) Mumbai-Kolkata via Nagpur (BSL-Durg)and Jabalpur (IT-JBP-KTE-ALD)
(4) HWH-Chennai (KGP-BZA)
(5) Mumbai-Chennai (Pune-Renigunta) This section was the only single line trunk route and it was thought that electrification and doubling should be carried out together.
All the projects Sl. No1-4 were completed in the early nineties except the IT-JBP-KTE-ALD route. There was change in Govt. and the new under the leadership of new RM priorities of IR shifted from national to regional. Several routes with very much lower freight traffic were indiscriminately getting electrified leaving this one in a quandary. The project was much hyped in late80s and early nineties almost 25 to 30 years before!, today it can just be called much delayed project.
With railways again shifting priorities from regional to national, now there is a ray of hope for the project which would have been completed by mid-nineties, to see the light of the day in coming years. Same is the case with Sl. No.-5 above. Railways is a huge organization, and it has reached ICU after suffering from several thousand or may several lacs of such incidences.