There shall be placed and thereafterward maintained warning signs on every highway or other way within the State approaching a crossing at grade of such highway or other way and the tracks of a railroad. Such signs shall be placed on each side of such crossing at such distances as shall be determined upon by the Department of Transportation which is required, and vested with authority, to cause to be located and maintained such warning signs. In the compact parts of cities and towns where the conditions mentioned in section 2920 exist and are observed and at all other places where in the judgment of the 2 commissions such signs are unnecessary, no such warning signs need be erected. [PL 1981, c. 698, §100 (AMD).]