Section 143(2) in The Punjab Motor Vehicles Rules, 1989
(2)The back of all seats shall be closed to a height of 400 milimetres above seats level:Provided that in the case of a single decked vehicle the State Transport Authority may specify the measurements within the above limits to which public service vehicles or a particular type of public works vehicle, shall conform in specific ares or on hill roads :Provided further than if the Government is satisfied that a particular vehicle or class of vehicles, having the internal height or head room measured along the centre of the vehicle from the top of the floor boards or battens to the underside of the roof supports in excess of the height specified in this rule, is suitable for carrying out any work in furtherance of a public purpose, the Government may, by notification in the Official Gazette, exempt such vehicle or class of vehicles from the provisions of this rule either generally or in such areas or on such routes subject to such conditions, if any as may be specified in the notifications.
