In case of oilers, tractors, rollers, dump wagons, and other road machinery and trucks, tractors, and trailers owned and operated by the federal government, a permit may be issued by the Commissioner of Motor Vehicles. The furnishing of a bond in such cases shall be in the discretion of such Commissioner. (Amended 1969, No. 212 (Adj. Sess.), § 6, eff. March 25, 1970.)