The long-awaited "Heritage Line" of Delhi Metro inched closer to being pressed into service, as the DMRC submitted papers to the safety department on Friday for approval -- the last step before the metro becomes available to commuters.

The Delhi Metro Rail Corporation (DMRC) submitted papers for the line connecting ITO and Kashmere Gate (5.17 km) to the Commissioner for Metro Railway Safety (CMRS) and also to the Independent Safety Assessor (ISA) for certification, after which the line will be opened to the general public.

"The documents will be scrutinised by CMRS office and thereafter a CMRS inspection will be planned. The line will be opened for public after safety certification of signalling system by the ISA," a statement issued by the transporter read.

A part of the Violet Line (ITO-Escorts Mujesar), the stretch was originally scheduled to be completed by December 2015 but missed several deadlines before its first trial-runs could be conducted in August last year.

"This was a challenging line from the very beginning. We had to execise extra caution during the construction because of the stretch being dotted with structures of historical value all along it. It also took us longer than usual time in getting clearance and securing landspace this time," a DMRC official told media.   

Given the recurring delays, he could not bring himself to commit to any time-frame and say when the metro would become commuter-ready.

"I cannot commit any time. Earlier, there have been instances when we were given permission in a day. Not sure about now, it may take month or even more," he said.