It's a pretty frequent problem for someone to be going 10mph below a 55mph limit. To pass safely you have to go well above the limit for a few seconds, even if they don't speed up, so that you aren't in the oncoming lane for too long.
If they speed up during the passing manoeuver you should probably slow down and fall back.
If there's oncoming traffic, sure, but not as a matter of principle. Once you start passing, you should definitely finish unless it becomes dangerous to do so.
If they speed up during the passing manoeuver you should probably slow down and fall back.
If there's oncoming traffic, sure, but not as a matter of principle. Once you start passing, you should definitely finish unless it becomes dangerous to do so.