When overtaking there are specifically one or two things that you need to do to make sure that you don't crash into the vehicle at the side of you
This weekend especially I've had the privilege of having 3 vehicles cut across lanes before pulling in past me. If it wasn't for me taking action and slowing down -- as well as furiously using my horn!! There would have been a major collision.
There we go ... in three simple words -use your mirrors - and this is the secret to not crashing into people whilst overtaking. When you are overtaking a vehicle the key to making sure that you have passed them is checking to see where they are.
Have they moved lanes? Have they sped up, because they don't want to be overtaken?
You need to know these things for definite before deciding whether it's safe to move back in.
If you are in a car with a rear view mirror the key to making sure it's safe before pulling back in is to make sure that you can see the car headlights that you're overtaking. So can you see his headlights in your rearview mirror?.If you can see his headlights in your rearview mirror, you know that the vehicle is far enough behind you to pull back in ....but you still then need to check the side mirror to make sure nothing else is approaching on the left hand side predominantly from sliproads or just somebody that's going past the vehicle.
If the vehicle that you're travelling in does not have a rear view mirror then the key again is using the same principle in the left hand side door mirror making sure that you can see the vehicles headlights that you're overtaking and then try and analyse is the vehicle in the same position is it getting closer is it falling further behind if the vehicles position is in changing or is getting closer it's not safe to pull back in if the vehicles position in the mirror is getting further back than you know that the gap has increased and that it is safe to pull back in