In the US and most of the world, hazardous materials placards do not carry words, only icons and numbers. So the question of language does not arise.
Placards are not used in maritime shipping of hazardous materials. Even in US ground transportation, placards are not required for the shipment of "Limited Quantities."
No. If you get into an accident, first responders are going to see the placards and assume the hazardous materials are loaded on the trailer. If you're in a state where you're unable to communicate with them, they're not going to be aware that there are hazardous materials in the cab of the power unit.
The DOT system of placards and labels classifies hazardous materials according to their type of hazard, i.e. radioactive, corrosive, flammable liquid, etc.
It's determined by weight. Gasoline is Hazard Class 3, which requires placards to be displayed if more than 1,000 lbs. of it is being transported. One gallon of petrol weighs between 5.8 and 6.5 lbs, so you'd be looking at 153 to gallons (roughly) before placards had to be displayed.
For detailed descriptions of the codes used follow the related link.
No, the placards on a military van container do not meet the requirement for placarding a vehicle. The vehicle itself must be appropriately placarded according to the hazardous materials regulations, which include displaying the correct placards based on the type and quantity of hazardous materials being transported. Simply having placards on the container is insufficient for compliance with vehicle placarding requirements.
The shipper is typically responsible for providing the required placards to the carrier transporting hazardous materials. Placards communicate essential information about the hazards present in the shipment and are required by transportation regulations to ensure the safety of the carrier and others on the road.
with the conductor or engineer
Hazardous material ceases to be hazardous when it is destroyed, sufficiently diluted in nonhazardous material, it is chemically changed into a nonhazardous material or incorporated into an object that immobilizes it and renders it unable to be hazardous.
Only if it's designed to carry more than 15 passengers (including the driver), or transporting an amount of hazardous material that it requires the display of placards under FMCSR.
Dangerous When Wet
which hazardous material can enter the body