What indicates that a vehicle is powered by alternative fuels?

A small placard on the rear bumper is a common indicator that a vehicle is powered by alternative fuels. This placard typically provides important information regarding the type of alternative fuel being used, such as compressed natural gas (CNG), propane, or electricity. It helps first responders, including firefighters, to quickly assess the vehicle's fuel type in case of an emergency, enabling them to take appropriate safety measures when dealing with such vehicles.

Other indicators like a bright colored flag can be used, but they are not universally standard, which means they may not be present on all alternative fuel vehicles. Similarly, while special license plates and emblems on the hood could denote alternative fuel usage, they are not as universally recognized or reliable as a rear bumper placard, which is specifically intended for notification during emergencies. Therefore, the presence of a small placard serves as an effective communication tool to alert responders about the vehicle's unique fuel system.