Why are placards used on vehicles transporting hazardous materials?

Placards are essential for ensuring safety in the transportation of hazardous materials. They serve as a visual warning to everyone nearby, indicating that the vehicle is carrying dangerous substances. This advance notice allows other drivers and emergency responders to recognize the potential risks associated with the materials being transported, which is crucial in preventing accidents or injuries in case of a spill or accident.

In contrast, the other options would not serve the primary purpose of placards. Indicating a speed limit does not relate to the hazardous nature of materials onboard. Specifying a route would not provide necessary information about the materials being transported, potentially leading to dangerous situations if the wrong routes are taken around populated areas or sensitive sites. Showing the driver’s qualifications is important for safety as well, but it does not inform the public or other drivers about the contents of the vehicle, which is why placards focus on communicating the presence of hazardous materials.