While driving, what does a 'head check' mean?

The concept of a 'head check' is crucial for safe driving, particularly when changing lanes or merging. It involves looking over your shoulder to ensure that there are no vehicles or obstacles in your blind spots, which are areas that cannot be seen through your side mirrors. By turning your head and checking your surroundings, you gain a clear view of the traffic situation behind you. This action helps prevent accidents that can occur when a driver assumes the lane is clear without confirming visually.

In the context of the other options, maintaining a still head at all times does not promote awareness of potential hazards, and relying solely on side mirrors may not provide complete visibility. Adjusting mirrors can enhance visual range, but it cannot substitute for the physical check that confirms there are no unseen vehicles in critical moments of driving. Thus, performing a head check is an essential part of defensive driving to ensure safety on the road.