Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 90, § 7T

The registrar shall adopt regulations establishing test procedures and instrumentation to be utilized for measuring sound levels of in-use vehicles. Such regulation shall include site criteria and moving and stationary vehicle measurement procedures and shall take into consideration accepted scientific and professional methods for the measurement of vehicular sound levels. The measurement procedures shall include adjustment factors to be applied to the noise limit for measurement distances of other than fifty feet from the center of the lane of travel and shall allow the extent feasible sound level measurement and enforcement action to be accomplished in reasonably confined areas such as residential areas of urban cities and off highway locations. Test procedures established by the registrar shall be in substantial conformance with applicable standards and practices established or recommended by the United States Environmental Protection Agency.