Section 156(1) in The West Bengal Motor Vehicles Rules, 1989
(1)If the holder of a permit relating to service of stage carriages or of contract carriages desires, at any time, to replace any vehicle covered by the permit by a vehicle of a different type or of a different capacity, he shall forward Part A of the permit and apply in writing to the Regional Transport Authority by which the permit was issued, stating the reasons why the replacement is desired and shall indicate the particulars of the vehicle to be replaced and of the new vehicle.
