Fog-induced poor visibility had claimed 15 lives last winter, between mid-January and mid-February. To avoid a repeat, the traffic department of the city police is providing its personnel with safety gear and has launched an awareness drive among pedestrians, especially morning-walkers, and motorists.

The haze, meanwhile, is continuing to take a disruption toll, with a helicopter carrying chief minister Buddhadeb Bhattacharya being forced to return to the city after failing to land in Malda on Sunday morning.

To battle the smoky veil on the ground, traffic cops are being supplied with torches and reflector jackets. ?Besides, we have readied a set of guidelines for pedestrians and motorists,? said deputy commissioner (traffic) Jawed Shamim.

The guidelines are based on the fact that mishaps at this time of the year take place mostly because people cannot see the road at a distance.

Visibility dips abnormally between mid-January and mid-February. ?We consider the period most dangerous and are urging people, especially morning-walkers, to keep as much distance as possible from the main carriageway,? Shamim added.

The traffic department has also drawn up a list of risky routes. ?All roads leading to and from Vidyasagar Setu, Red Road and other thoroughfares passing through the Maidan, Park Circus-EM Bypass and Kasba connectors figure on the list,? said an officer.

The Bypass, VIP Road and Rajarhat Expressway are other perilous pathways.

The victims last winter included three constables. ?Most mishaps occurred either late at night or in the early hours. Some of the bodies were found on the side of the road, suggesting that the victims had not violated any traffic rule but that the drivers had failed to spot them in the fog,? said an officer.

Police said the helicopter carrying the chief minister to Malda took off around 10 am but could not land there because of dense fog.

A Mumbai-Calcutta Air-India flight was another casualty. The plane was to land here at 2.15 am, but had to fly back because of poor visibility. It returned to the city later. All morning flights were delayed by half an hour.

Met officials said the fog was caused by heavy incursion of moisture from the Bay of Bengal, following the development of an upper-air circulation over Bangladesh.

The upper-air circulation has also changed the wind pattern. ?The North Wind has become weak, resulting in a rise in the minimum temperature,? said an official. ?The foggy spell will continue, but the intensity is likely to weaken in the next 24 hours. The minimum temperature on Sunday was 14.3 degrees, which is normal. We expect it to fall by another degree on Monday.?