Section 39(4) in The Static and Mobile Pressure Vessels (Unfired) Rules, 2016
(4)Design safety requirements-General :(i)There shall be a clear space of at least 15 cm between the back of the cab and the front of the vessel.(ii)The rear of the vessel shall be protected by a robust steel bumper and this bumper shall be-(a)attached so that collision stresses will be transmitted to the frame work of the vehicle or, in the case of an articulated vehicle to the frame work carrying the wheels of the vessel(b)situated at least 7.5 cm to the rear of the rear-most part of the vessel ;(c)extended on each side of the vehicle to at least the maximum width of the vessel.(iii)the maximum weight of the liquefied gas for which the vehicle is designed should not exceed the difference in weight between the unladen weight of the vehicle and the maximum gross weight permitted for that class of vehicle under the appropriate transport regulations.
