When you are preparing to change lanes on a roadway or turn at an intersection you must check your blind spots by?

When preparing to change lanes on a roadway or turn at an intersection, you must check your blind spots by turning your head about 90° left or right.

By turning your head 90°, you can use your eyes to scan from the front side of the car to the back side of the car, and you will still be able to see the road in front of you using your peripheral vision. It is important to only turn your head to check your blind spots, not your whole body.