What should you do before changing lanes?

Before changing lanes, it's essential to check both mirrors and blind spots because this ensures you are aware of the surrounding traffic and any potential hazards that may not be visible in your direct line of sight. Checking mirrors helps you see vehicles that might be approaching from behind or next to you, while checking your blind spots is crucial since not all vehicles are visible in mirrors. This practice significantly reduces the risk of collisions and improves overall safety on the road.

The other choices focus on incomplete or less effective practices. For instance, signaling is important, but doing so without checking your surroundings can lead to dangerous situations. Relying solely on the rearview mirror fails to account for vehicles that may be in adjacent lanes. Looking for traffic signs is a good practice, but they do not directly pertain to the immediate action of changing lanes. Hence, the comprehensive approach of checking mirrors and blind spots is the safest and most effective strategy.