Sub section (6) of section 63 of the Act with which we are concerned in this case reads thus: "(6) Notwithstanding anything contained in sub section (1), but subject to any rules that may be made under this Act, the Regional Transport Authority or any one region may, for the convenience of the public, grant a special permit in relation to a public service vehicle for carrying a passenger or passengers for hire or reward under a contract, express or implied, for the use of the vehicle as a whole without stopping to pick up or set down along the line of route passengers not included in the contract, and in every case where such special permit is granted, the Regional Transport Authority shall assign to the vehicle, for display thereon, a special distinguishing mark in the form and PG NO 454 manner specified by the Central Government and such special permit shall be valid in any other region or State without the countersignature of the Regional Transport Authority of the other region or of the State Transport Authority of the other region or of the State Transport Authority of the other State, as the case may be.