Final answer:
To check traffic when backing up, use your mirrors and physically look behind you to cover blind spots.
Step-by-step explanation:
When backing up, it is important to check the traffic to ensure safety. To check traffic, you can use your rearview and side mirrors to look for any approaching vehicles. Additionally, you should also turn your head and physically look behind you to cover blind spots. This is especially crucial when backing up in crowded areas or when reversing out of a parking spot.