Section 120(2) in The West Bengal Motor Vehicles Rules, 1989
(2)Special condition of permit for motor cab or a metered taxi. -(a)No Contract Carriage permit for a motor cab or a metered taxi, whether issued by Regional Transport Authorities or by the State Transport Authority shall be granted in respect of a motor vehicle which is more than 5 years only on the date of initial grant of permit.(b)Where a vehicle covered by such a permit, is proposed to be replaced by another, the latter vehicle shall also not be more than five years only on the date of such replacement.(c)Such permit shall be deemed to be invalid from the date on which the vehicle covered by the permit completes 15 years. unless the vehicle is replaced :Provided that the State Government may, by order constitute Board for [Kolkata] [Substituted vide section 5 of the West Bengal Capital City (Change of Name) Act, 2001 (West Bengal Act 18 of 2001) (w.r.e.f. 1.1.2001) for the word 'Calcutta'.] and for the Districts separately, consisting of experts and such other persons as it may deem fit, and all such motor vehicles completing 15 years shall have to obtain approval from such Boards so constituted for their respective areas, for being used as motor cab or metered taxi. The Board so constituted shall accord approval for such period as it may deem fit not exceeding two years at a time and the total period of extension by such Board shall, in no case, exceed five years beyond the period of 15 years :Provided further that the State Government may, review this sub-rule from time to time and may, by order vary the time period as stipulated in the proviso to sub-rule (c). The existing motor vehicles, used as motor cabs or metered taxis, which are more than 15 years old and which are covered by such Contract Carriage permits, shall also be governed by the clauses (a), (b) and (c) of this sub-rule.Explanation. -For the purposes of clauses (a), (b) and (c) of this sub-rule, the period of 5 years, or 15 years, shall be computed from the date of initial registration of the vehicle.
