Maryland has restrictions on Propane in the Tunnels, Go around Baltimore on the Key Bridge or Rt. 301.
Code of Maryland Regulations (COMAR)
govern the transport of hazardous materials across our toll facilities. Under these regulations, vehicles carrying bottled propane gas in excess of 10 pounds per container (maximum of 10 containers), bulk gasoline, explosives, significant amounts of radioactive materials, and other hazardous materials are prohibited from using the Fort McHenry Tunnel (I-95) or the Baltimore Harbor Tunnel (I-895). The Francis Scott Key Bridge (I-695, the Baltimore Beltway) is a convenient alternative route for crossing Baltimore's Harbor.
Not sure what designates significant amounts of Radioactive Materials