Tunnel, Bridge, and Railroad-Crossing Restrictions; Hazmat Routing
What this domain covers
Where a placarded or PIH vehicle may go, what it must do at a grade crossing, and how tunnel and bridge restrictions change the plan.
Railroad crossings (49 CFR 392.10)
Placarded vehicles stop within 50 feet but not less than 15 feet of the nearest rail, look and listen both ways, and cross only when the far side has room. Cross in the same gear - no shifting. Crossings posted “Exempt” are the main exception. Never stop on the tracks.
Tunnels
Many tunnels ban all hazmat; others ban only explosives, PIH, and flammable gases. Restrictions are posted at the entrance and listed in the state route table - check before you commit, not at the portal. If permitted, turn on flashers, keep moving, and never stop inside.
Bridges
Watch weight limits, clearance, and any hazmat prohibition. A bridge limit applies to your scaled axle and gross weights, not your registered weight.
Routing (49 CFR 397.3)
Carriers must follow state and local hazmat route designations. Routes are chosen to avoid congested areas, tunnels, and residential streets where a designated alternate exists; unnecessary stops and detours are violations and add risk.
Worked example
Your shortest route runs through a tunnel posted “No Hazardous Materials.” You carry twelve 55-gallon drums of Class 3 - about 660 gallons, well over the 1,001 lb placarding threshold. The load is placarded, so the tunnel is off-limits and you must take the state-designated alternate. A GPS suggestion is not a defense.
Traps
Treating a tunnel ban as explosives-only; stopping 10 feet from the rail (too close) or 60 feet (too far); entering a crossing before the far side clears; and ignoring bridge weight limits because the truck “looks fine.”