What should you do before changing lanes?

Before changing lanes, it's crucial to check your mirrors and signal your movement because this action ensures that you are aware of your surroundings and communicate your intentions to other drivers. Checking mirrors allows you to see vehicles that may be in your blind spots or approaching quickly, which is essential for making a safe lane change. Using your turn signal is equally important as it alerts other road users of your upcoming maneuver, helping to prevent potential collisions.

The other options do not address the fundamental safety measures required before changing lanes. Making sure your radio is off does not directly contribute to lane change safety. Relying solely on side mirrors does not provide a complete view of the road, leaving blind spots unmonitored. Adjusting your speed significantly without reason may confuse other drivers and can lead to hazardous situations. Thus, the safest and most responsible practice before changing lanes involves checking mirrors and signaling your intentions.