The promise of a Metro train every six minutes has fallen flat because of a dated signalling system on most of the stretch and malfunctioning doors of rakes that are fit to be discarded.
The Metro authorities had announced that trains would run at six-minute intervals between 9am and 8pm on weekdays from March 31. To enable the change, the number of daily rides has been increased from 236 to 270.
“Trains are leaving the originating stations in time but mostly wrapping up the trip two-three minutes late,” said a senior Metro official who refused to be named.
“We are trying to make up for the delay by reducing the halt at the stations that record less footfall but the six-minute interval still remains a dream for most part of the stipulated 12-hour duration.”
The official cited several reasons for the late running of trains — the old block signalling system on the underground stretch, problems caused during the passage from the new automatic signalling zone to the block signalling one and the malfunctioning doors of old rakes.
The automatic system was made operational on the elevated stretch (8km) between Tollygunge and Kavi Subhash (New Garia) stations on Sunday but teething problems disrupted the service on the first day of the switchover.
Dum Dum-bound trains had to stop at the signal on the approach to Tollygunge from Kudghat, where the 17km block signalling zone starts.
“Work on the change in the signalling mode had at times forced us to take recourse to the paper line clearance system at some stations on the elevated stretch last week, which delayed trains. The same happened on the underground stretch today because of a glitch in the block signalling system,” the official said.
Paper line clearance is the manual go-ahead given to the driver to start his rake when the signalling system has conked out.
A station manager fills in a form, asking the driver to leave. The driver takes the document after signing on the counterfoil and conveys the “consent to leave” to the guard, who gives the final clearance for the rake to start.
“The whole process takes a lot of time and you can’t run trains punctually banking on this system, especially when the gap between two trains is to be as short as six minutes,” the official said.