Because the Selectmen did not follow proper regulatory procedures, the speed limit signs in question are demonstrably illegal and unenforceable. Engineering data on file for each speed zone throughout Massachusetts justifies the posted speed limit in each area. This information essentially validates the posted speed limit by virtue of its existence. It follows that the lack of any requisite speed study engineering data on file invalidates the posted speed limit. Such is the case with the sixty (60) phony speed limit signs posted by the Selectmen. The Selectmen’s choice to bypass this regulatory approval process is ultra vires, and renders these signs illegal and unenforceable by definition.
MassHwy, acting in accordance with the authority granted by G.L. c. 90, § 18 and related statutes, has established regulatory procedures for the posting of speed limits within the Commonwealth. These procedures are set forth in Procedures for Speed Zoning (MassDOT), which reads in relevant part as follows:
Chapter 90, Section 18 authorizes the posting of numerical speed limits on all roadways in Massachusetts. The foundation for the actual posting of a speed limit is a thorough traffic engineering study. After a study has been completed, a Special Speed Regulation is drafted and approved by the governing authority of the roadway, the Registry of Motor Vehicles and MassHighway. All posted regulatory speed limit signs must adhere to this approval process. If a speed limit is posted without this procedure, it is in violation of Chapter 90, Section 18, and is therefore considered illegal and unenforceable.