No person shall be liable to penalty under the four preceding sections for violation of a by-law relating to travel on a bridge, unless a white board containing in black letters the substance of said by-law is kept posted in a conspicuous place at each end of the bridge.
Mass. Gen. Laws ch. 85, § 24
Posting of regulations on bridges
Official source: Massachusetts Legislature. Reproduced from public-domain Massachusetts statutes; confirm against the official source for the current text. Not legal advice.