It may be noted that once the talgo rake reach mumbai at the end of a trial, it has to be brought back to Delhi any how without any financial and r&D benefits.
If Technical Parameters of both up and down tracks get checked and validated instead of just only one track, that too without any additional cost and time, what is the loss? there are only the benefits.
The opportunity of checking the Mumbai-Delhi line also at no additional cost and time investment is lost.