Section 133(1)(c) in The West Bengal Motor Vehicles Rules, 1989
(c)that the service shall be regularly operated on the specified route in accordance with the approved time-table except,(i)when prevented by accident, unmotorability of the route or any unavoidable cause, or(ii)which otherwise authorised in writing by [the Regional Transport Authority;] [Substituted vide clause (3)(a) of the Notification No. 7221-WT/3M-151/96 dated 28.9.2001 for the words 'the Regional Transport Authority.'.]