Fog enveloped Delhi on Saturday. Thirty-six trains will arrive late, two have been rescheduled and 13 cancelled due to low visibility or operational reasons The national capital has been experiencing bitter cold since the last few weeks, leading to cancellation and rescheduling of trains. Early morning #Visuals of fog from Delhi's India Gate and Rajpath area pic.twitter.com/vfzHb7OlMs — ANI (@ANI) December 30, 2017 × Pollution seems to have worsened the situation. The Air Quality Index, an indicator of air pollution, at the capital's Lodhi Road area, remained in the "very poor" category, ANI reported. During fog, visibility becomes very low and trains have to run at a highly-restricted speed to ensure the safety of the passengers causing considerable delays in their movement.