Each year, close to 2 billion tons of hazardous materials are produced in the United States. The amount of hazardous materials shipments that are shipped each year is approximately three billion tons. Each shipment will be moved several times before reaching its destination. Bulk transportation of hazardous materials includes overland shipping by tanker truck and rail tank car, and by special containers that are loaded onto vehicles. Over water, ships loaded with specialized containers, tanks, and drums are used. In small quantities, hazardous materials require specially designed packaging for truck and air shipment.