Why are placards used on vehicles?

Placards are essential tools for communication on vehicles, particularly those transporting hazardous materials. They serve primarily to communicate risk by indicating the specific type of hazardous material being carried. This is critically important for safety regulations and emergency response. For instance, if a vehicle is transporting a flammable substance, the placard provides immediate information to first responders and others about the potential dangers in case of an accident or leak.

The other choices do not align with the primary function of placards. They do not indicate the make and model of the vehicle, display personal driver information, or show weight limits, which are addressed through different means such as vehicle registration, licensing, or weight signage. Hence, the use of placards is uniquely centered on the communication of potential hazards associated with the materials being transported.