Final answer:
The red edged, orange triangular sign on the back of some vehicles indicates that the vehicle is a slow-moving vehicle.
Step-by-step explanation:
The red edged, orange triangular sign on the back of some vehicles indicates that the vehicle is a slow-moving vehicle. It is commonly known as a slow-moving vehicle emblem or a SMV emblem.
This sign is used to warn other drivers that the vehicle is traveling at a slow speed and they should use caution when approaching or overtaking it.