A fog-affected train is a train that is delayed or affected by foggy weather conditions. When there's fog, it can be hard for the train driver to see the tracks clearly, which slows down the train or even stops it for safety reasons. This delay can happen because the train needs to go slower to avoid accidents.
During foggy weather, the sight becomes blurry, and due to that, trains need to run at a very controlled speed to ensure passengers's safety, which leads to considerable delays in the running of trains.
Fog diminishes visibility; that's why train drivers run slowly to make sure they can see the track-side signals, keeping passenger safety on top priority. They stop or move on as per the signal light.
If a train gets cancelled due to fog, the passenger will be granted a full refund, whether they have booked online or through the PRS counter. The passengers are advised to check the live running status of their train before commencing their journey.