"Since 1984, Utahns in the densely populated Salt Lake, Davis, Utah, and Weber counties have taken their cars in for mandatory emissions testing every two years. Utah is unique in that it requires smog checks only in the counties that are the worse offenders, due to the number of cars they have on the road, rather than requiring these tests statewide."
The above statement is from the Utah DMV site. As I read it if you have a car registered in any county except the above four there is no smog test done....Damn....
LARRY