Uttarbanga Exp: উত্তরের আত্মার আত্মীয় - Avinaba Bose

Not exactly. The term was very commonly used in the USA also. But it is not popular outside India now and RF's too tend to avoid using the term in other countries. It is technically called a 'Pilot'.
These are not old locos actually. WDP1 class is actually younger than the WAP4/WAP5 and WAG9. :)
They had some innovative designs like using a Bo-Bo bogie arrangement and fabricated bogies instead of the traditional ALCO bogies. They were supposed to follow the ideal passenger...
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loco specifications like the WAP5. But the locos had many ride quality issues. May be DMW is upgrading these to similar specs like the WDM3D. Hopefully they will overcome their issues now and deliver true high speed action that there were designed for ( Targeted at 140kph originally, but could achieve only 120).
As to the need of the upgrading these locos, even if IR is electrified more, there will be considerable diesel action under the wires. A fully electrified network will not be economical or energy-efficient and even though IR's actions seem to be in the opposite direction, a lot of people within IR acknowledge that diesel traction is still extremely essential. These locos in particular can now offer faster runs on the minor routes and will be very useful for passengers and short distance express trains. I hope BZA's WDP1's are too upgraded this way.