This is the moment a man dangling out of a train door in South Africa slaps an unaware commuter standing on the platform.<br /><br />Video filmed at Kaalfontein station in Gauteng shows the packed Metrolink train from Johannesburg to Tembisa pulling away from the station.<br /><br />Out of nowhere, an unknown man reaches out and lands a slap on the commuter's face. <br /><br />The filmer claimed slapping is a "common" occurrence.