Judgment

CHINNAPPA REDDY, J. :- In these writ petitions, the vires of conditions No. 18 attached to the permits issued by the respective Regional Transport Authorities of the State of Uttar Pradesh to the petitioners for plying contract carriages known as mini buses is in question. Mini bus is defined by Sec. 2 (d) the U.P. Motor Vehicles (Special Provisions) Act, 1976 as meaning "an omnibus which is constructed or adapted to carry not more than 35 persons excluding the driver." Section 51 (2) of the Motor Vehicles Act enables the Regional Transport Authority granting a contract carriage permit to attach in the permit any one or more of the conditions enumerated in that provision. Item (x) of Section 51(2) reads "any other condition which may be prescribed." Condition No. 18 is a condition which is prescribed and attached, in every permit for plying a mini bus. The condition in its original form stood thus. "The motor vehicle covered by the permit shall not be more than four years old counted from the date of registration to any time during the validity of the permit." The period of four years originally stipulated was increased to "seven" on September 28, 1978 and again raised to "