Yep, I see ATV's/UTV's running down the roads in Pa. all the time. Bunches of them riding together sometimes and pulling into stores and gas stations to refuel. So much so that I thought maybe it was legal. They are not legal on the roads here in NY but people run them on back roads all the time anyway. Sometimes a cop will nail you for it while I've seen others ignore it. Just depends on the cop and his mood at the time I guess but more often than not they seem to ignore so long as it's on a rural back road.
