These petitions filed under Article 226 of the Constitution pray for the issue of writs of mandamus or other appropriate writs, directions or orders directing the respondent, the State of Madras, to forbear from enforcing the provisions of the Madras Motor Vehicles (Taxation of Passengers and Goods) Act, 1952 (Act XVI of 1952) or the rules framed thereunder against the several petitioners. A common question of law arises in all these petitions concerning the legality and constitutional validity of the said Act (which will be hereafter referred to as the Act.) The petitioners carry on the business of motor transport in different areas in the State. They are governed by the provisions of the Motor Vehicles Act, 1939. In respect of the motor vehicles employed in the business of the petitioners and which ply for hire they are subject to the tax levied under the Madras Motor Vehicles Taxation Act (Madras Act III of 1931). The vehicles run under permits issued under the Motor Vehicles Act, 1939, subject to the conditions imposed under the licences and by the other provisions of the Motor Vehicles Act. Section 43-1(ii) empowers the Government of the State to fix minimum