I asked the MDTA about the weigh stations on I-95 in Maryland at the Perryville, Maryland location. Signs say all vehicles over 5 tons must stop when scales are open.
Here is their reply:
Thank you for your email and for contacting the Maryland Transportation Authority (MDTA). Financed solely by toll revenue, the MDTA is an independent State agency that finances, owns, operates and maintains the State's eight toll facilities. We appreciate your bringing this matter to our attention. All vehicles with a gross vehicle weight or gross vehicle weight rating of greater than 10,000 pounds must stop at open weigh stations. Only vehicles that are operating in commerce may be subject to a safety inspection.
Thank you again for your email, and please let us know if we may assist you further. Kerry Brandt Division of Communications
Just thought I would pass this along.