To ensure a lane is clear before changing lanes, what should you do?

To ensure a lane is clear before changing lanes, it is essential to look over your shoulder into the lane you want to enter. This action allows you to check for any vehicles or obstacles that may not be visible in your mirrors. While mirrors provide a view of the traffic behind and to the sides of your vehicle, they cannot capture areas known as blind spots—regions adjacent to your vehicle that are not visible through mirrors alone. By physically turning your head and looking, you gain a fuller understanding of the driving environment and can make a safer and more informed decision to change lanes.

Other methods, such as checking mirrors or signaling, play important roles in lane changes, but they can't replace the necessity of checking blind spots. Signaling your intention to change lanes helps inform other drivers but does not ensure that the lane is clear. Similarly, slowing down can alter your vehicle’s position and interactions with other drivers, but it does not provide a confirmation that the lane is vacant. The comprehensive check that involves looking over your shoulder is the most effective way to guarantee safety when changing lanes.