Highway Patrol Officer Rod Elmer says it never takes long to find violators in the carpool lanes on Interstate 15. After all, state studies show that about one of every five cars there is breaking the law. He entered the freeway Thursday morning at the 400 South entrance in Salt Lake City, which is supposedly just for people who qualify to use express lanes either with two riders, a toll transponder or a âC decalâ for clean-fuel cars.