The travel time will come down from 30 minutes to five.
Part of the site falls in the jurisdiction of the Railways and the Northern Railways are building it on the behalf of the Delhi Development Authority (DDA).
Cyclists and pedestrians will also be able to move through this underpass.
The proposed underpass crosses the busy Delhi-Mumbai rail route used by 300 trains a day.
The work below the Railway tracks is being executed without disrupting the rail traffic.
But the project — planned in 2008 — is running behind schedule and construction work has caused chaos with the commuters facing a tough time.
Since the project started, its design has been changed many times.
Work began only in 2009 and the initial cost of the project has more than doubled from Rs. 127 crore to nearly Rs. 300 crore.
The DDA has blamed the Northern Railways for the delay.