Chapter 160 of the General Laws is hereby amended by inserting after section 19 the following section:-

Section 19A. Notwithstanding any general or special law to the contrary, a city or town may, by vote of the city council or other legislative body of a city, or town meeting or other legislative body of a town, establish designated school zones as provided in section 2 of chapter 85 for passenger and freight locomotive engines operating on railroads within the city or town, and may set speed limits for locomotives operating in said zones at a rate of speed not to exceed 20 miles per hour; provided, however, that no such designation or speed limit shall be effective until the city or town; (i) notifies any railroad corporation with a railroad running through the designated zone of such designation and speed limit, and (ii) erects signs indicating such designation and speed limit, in a manner consistent with the department of highways’ current manual on uniform traffic control devices and said department’s sample regulation for a standard municipal traffic code, at such points as said department and the effected railroad corporations, acting jointly, may designate. No railroad corporation, including the Massachusetts Bay Transportation Authority, shall permit a passenger or freight locomotive to operate on a railroad at a rate of speed greater than the rate posted while traveling through a designated school zone in a city or town. Cities and towns shall be responsible for the cost of erecting and maintaining signs pursuant to this section.