Police told the dpa news agency that the 61-year-old victim had refused to put out his cigarette when the older man informed him he was smoking in a non-smoking part of the Friedrichstrasse station Monday morning.
They say the older man then hit him in the face with the wooden board, injuring his upper lip.
Police, who apprehended the attacker at the scene, say he had the wooden picket on hand because he was on his way to his garden.
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