Trains on the Violet Line crawled during the morning rush hours due to a major signal failure, while services on Blue Line remained affected for over two hours due to flashing of the OHE (overhead wire) near the Karol Bagh station at around 2.40 pm.
A Delhi Metro Rail Corporation (DMRC) official said services slowed down at around 8 am along the entire Violet Line, stretching between Faridabad and Kashmere Gate, after trains lost touch with the control centre.
"The issue was resolved at 9 am and trains are now being regulated as per normal schedule on Line-6," the official said.
Later in the day, it was the turn of Blue Line, the metro's longest and busiest corridor, which connects Noida and east Delhi's Vaishali to west Delhi's Dwarka.
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"Services on this line were affected between 2.40 pm and 4.13 pm due to point flashing -- a signaling issue in which trains don't attain normal speed and have to cross the point area with restricted speed as a safety measure. This led to bunching of trains during this period," an official said.
The Operational Control Centre is considered the nerve- centre of the metro network, and following the incident, the alternative mechanism of station-level handling was activated.