Final answer:
After passing a car, it's safe to return to your lane when you see its headlights in your rearview mirror, confirming enough space for a safe lane change.
Step-by-step explanation:
After passing a car, it is safe to return to your driving lane when you can see the headlights of the passed car in your rearview mirror. This representation ensures you have enough distance between your vehicle and the car you just passed, providing a safety cushion and preventing you from cutting the other driver off as you re-enter your lane. It's important to note that relying on another driver to signal you to move back into your lane is not a safe practice, nor is it enough to only signal your own intention to return to the lane. Adequate visual confirmation is crucial for safety.