A 22-year-old carnival worker in Idaho blames two friends having sex in the back seat of his car for an accident in which the car struck a telephone pole.

Joshua Frank pleaded guilty today to a misdemeanour charge of failing to notify a police officer of a traffic accident. He left the vehicle at the site of the crash. He was fined $US188 ($A221), the Lewiston Tribune reported.

According to a probable cause affidavit, Frank told police the actions in the backseat caused the car, which "was top heavy anyway," to become "tippy" and lose control.