Depends on how many lanes there are. For example:
-the freeway here has a maximum speed of 60, and a minimum speed of 50. So, I sit in the left lane and P&G between those two speeds for an average of 55 mph. There is ample room for people to overtake so I don't sweat driving under the limit.
-On a one or two lane road, it gets a little trickier. If the limit is say 30, I'll P&G between 27 and 33 because those are the variations in speed that motorists tend to have anyway. If the person behind is particularly impatient I will just P&G between 30 and 33, if conditions permit.
It is a tough one, I hate being 'that guy' but if you are courteous enough I don't see it being a problem.
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