The provisions of 720 CMR 9.08(4)(a) shall not apply to persons operating federal, state or municipally owned vehicles carrying such dangerous articles as may be required during an existing or impending emergency nor shall they apply to any vehicle carrying a flammable liquid of a type which is required for the propulsion of the vehicle and is in a portable container in a quantity not exceeding 15 gallons or in a tank which is an integral part of the vehicle, nor shall it apply to devices in a quantity not exceeding 12 devices to be used for the sole purpose of warning other motorists of an emergency condition.
The provisions of 720 CMR 9.08(4)(a) shall not apply to persons operating a vehicle transporting radioactive material when such radioactive material is such that it is exempt from all I.C.C. specification packaging, marking, and labeling because of type and quantity nor shall they apply to persons operating a vehicle transporting radioactive material which consists solely of manufactured articles, other than liquids, when the gross weight of such radioactive material and its container does not exceed 500 pounds per vehicle.
The provisions of 720 CMR 9.08(4)(a) through (c) shall not apply to any vehicle carrying a compressed natural gas of a type which is required for the propulsion of the vehicle, provided the tunnel exhaust fans are in operation, and so long as said vehicle has a maximum fuel capacity consistent with safe practice and national standards including Federal Motor Vehicle Safety Standards #303 and #304, and is equipped with excess flow valves for fuel lines with an inner diameter larger than 1/2", and is identified by a blue-and-white diamond-shaped decal attached as specified in NFPA 52, and is not used to transport compressed natural gas in commerce.
720 CMR, § 9.07