Idaho Code § 49-639
On a two-lane highway outside an urban area where passing is unsafe due to oncoming traffic or other conditions, the driver of a vehicle traveling slower than the normal speed of traffic and behind which three (3) or more vehicles are formed in line shall turn off the roadway at the nearest place designated as a turnout or at the next available location where it is safe and reasonable for the vehicle to be pulled over in order to permit the following vehicles to pass. Such driver shall not be deemed to violate this section if he has not, during the time when three (3) or more vehicles are formed in line behind his vehicle, passed a designated turnout or location where it would be safe and reasonable for the vehicle to be pulled over.
Idaho Code § 49-639