NEW DELHI: Thousands of passengers were stranded as nearly 400 trains were delayed due to dense fog across the country on December 31.

According to the official data, as of December 31 midnight, 400 mail and express trains reached their destinations late after getting delayed on account of fog.

As of January 1, 2018, 6:30am, 56 trains arrived late, 20 were rescheduled and 15 trains were cancelled.

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The Railways said that it has started Fog Pass Device (Fog Pilot Assistance System) or FSD, which is is GPS-enabled and can continuously calculate the distance of the train in relation to the next landmark, enabling drivers to know when exactly a signal is approaching.

The national transporter has recently installed 4,920 such devices in the most fog-affected railway zones - northern, north-central, north-eastern and north-western.

Plans are afoot to install additional 1,175 such devices to take the total to 6,095, covering the most-affected zones, the national transporter said.