According to DOT regulations or state law, how should vehicles transporting cylinders be marked when the total weight exceeds 1000 lb?

When transporting cylinders, vehicles that exceed a total weight of 1,000 pounds are required to be placarded in accordance with DOT regulations. Placarding serves a critical safety function, as it provides important visual information to emergency responders and others about the nature of the cargo being transported. This includes identifying hazardous materials, which in the case of propane can pose risks such as flammability or explosion.

The use of placards helps ensure that drivers and first responders are aware of the potential dangers, allowing them to take the necessary precautions in the event of an accident or emergency. Such regulations are designed to promote safety in transportation and minimize risks associated with transporting hazardous materials.

In this context, the other options would not meet safety standards or regulatory requirements. Being unmarked or using standardized labels alone does not provide adequate warning about hazardous materials, while color-coded signs do not conform to the specific requirements set by DOT regarding the transportation of hazardous substances. Therefore, proper placarding is the correct and legal method for marking these vehicles.