law: 72. Defacing public notices.
  If any person without lawful authority
  (a) in this behalf pulls down or wilfully damages any board or documents set up or posted by the order of the metro railway administration on the metro railway, or any rolling stock, or
  (b) obliterates or alters any letters or figures upon any such board or document or upon any rolling stock,
  he shall be punishable with imprisonment which may extend to two months or with fine up to two hundred and fifty rupees, or with both.