Final answer:
A red-edged, orange triangular sign on a vehicle is a hazard sign indicating a slow-moving vehicle. It serves as a cautionary symbol for other drivers. The sign's bright colors enhance visibility for safety purposes.
Step-by-step explanation:
The red-edged, orange triangular sign on the back of some vehicles is a hazard sign that typically indicates the vehicle is slow-moving. It’s commonly found on agricultural machinery, construction equipment, or any vehicle that cannot reach the minimum speed for highways. The bright color is highly visible and the triangular shape is an international symbol for caution, alerting other drivers to slow down and take care while passing. The use of high-visibility colors like orange is intentional to ensure that the sign captures attention in various light conditions. The red border enhances this effect, making it easy to see and recognize.