Once you have passed a vehicle and are preparing to return to your original lane, give yourself enough space to be sure that you’re not going to clip the front of the vehicle you’re passing. That’s why they call it “passing” and not “clipping”. To be sure that you’re far enough head, try looking in your rear view mirror until you can see both of the car's headlights. This way you can be sure that it’s well enough behind you. If you’re looking and looking but still don’t see the headlights, chances are good that you ran that vehicle off the road and into a ditch. In that case, it is now safe to return to your original lane.