Final answer:
If a load extends 4+ feet beyond the bed or body of a vehicle driven on a highway, it must be marked with warning flags. At least one bright red or orange flag should be used and securely fastened to the extreme rear of the load.
Step-by-step explanation:
According to the guidelines set by the Federal Motor Carrier Safety Administration (FMCSA), if a load extends 4+ feet beyond the bed or body of a vehicle driven on a highway, it must be marked with warning flags.
The FMCSA requires at least one warning flag to be used to mark the load, regardless of its length. The flag should be bright red or orange and at least 18 inches square. It should be securely fastened to the extreme rear of the load to provide warning to other road users.