Which hazmat loads require a driver to notify and get permission from local authorities before entering a tunnel?

TUNNEL AND BRIDGE RESTRICTIONS for hazardous materials are imposed by state and local authorities to protect infrastructure and the public from catastrophic incidents. MOST RESTRICTIVE: CLASS 1 EXPLOSIVES (Divisions 1.1, 1.2, 1.3) — the highest-consequence hazmat loads are the most restricted; many major tunnels (Lincoln Tunnel, Holland Tunnel in NYC; Baltimore Harbor Tunnel; etc.) are closed to explosives above very small quantities; some prohibit all Class 1.1/1.2/1.3 shipments; PROCESS FOR PERMITTED LOADS: Contact the authority controlling the tunnel (state DOT, port authority, etc.) in advance — not at the entrance; obtain written permit and any escort requirements; follow approved route (may require off-peak hours, police escort, specific lane); ROUTE PLANNING: Drivers must know tunnel restrictions on their planned routes; HazMat route plans (required for Class 1.1/1.2/1.3) specify approved crossings; GPS may not know all tunnel restrictions — paper route planning with verified crossing information is the professional standard; CLASS 2.3 (Poison Gas): Also restricted from many tunnels; OTHER CLASSES: Typically may use tunnels, but check local regulations for specific tunnels; some tunnels restrict flammables above certain quantities; VIOLATION RISK: Entering a restricted tunnel is a federal/state violation and risks permit revocation, significant fines, and — in a worst case — catastrophic incident responsibility.