Section 239(1)(iv) in The West Bengal Motor Vehicles Rules, 1989
(iv)in the case of a double-decked vehicle with an uncovered top-deck, the top-deck shall be provided with side and end rails, the top of which shall be at least 91 centimetres above the deck boards or battens at the sides and 46 centimetres above the highest part of any seat, and that top of the front and back rails shall be at least 99 centimetres above the deck boards or battens and shall follow the camber of the deck.