Section 51
SEC. 51. No provincial, city or municipal authority shall regulate or restrict the rate of speed or allowable gross weight of motor vehicles within their respective jurisdictions otherwise than in conformity with the provisions of sections twenty, twenty-one and twenty-six of this Act: Provided, That the Director of Public Works or his deputies may limit the gross weight and maximum speed of any vehicle crossing a bridge or ferry, or operating on any designated section of a highway to a value consistent with the safety or preservation of such bridge or ferry or highway.