At what point do you feel like you need to pull off of the road because you're going too slow for traffic? Obviously lots of factors involved here, but imagine a 3 lane road varying from a 35-40mph speed limit, and remember some people will do 45-50 anyway.

I feel fine above 16 mph, but as soon as I dip to 15 or 14, I want to pull off on to the sidewalk and take a breather.