Have you ever been told not to cross the yellow line on the platform, specially when a train enters the station? Do you know the reason why the yellow line exists? If you stand too close to an incoming train, there is a possibility that you might get sucked in between the train and the platform. The reason is very simple. When a train comes into a station it displaces air around it and creates a temporary vacuum. Objects (including you) which are placed close to the incoming train tend to get sucked into the vacuum. So as a safety measure the railway authorities have drawn an yellow line on every platform. Greater the speed of the train higher is the possibility of such an event. So next time when you are at the station, watch out for the yellow line!