321.323A  Approaching certain stationary vehicles.
  1.  The operator of a motor vehicle approaching a stationary authorized emergency vehicle that is displaying flashing yellow, amber, white, red, or red and blue lights shall approach the authorized emergency vehicle with due caution and shall proceed in one of the following manners, absent any other direction by a peace officer:
  a.  Make a lane change into a lane not adjacent to the authorized emergency vehicle if possible in the existing safety and traffic conditions.
  b.  If a lane change under paragraph “a” would be impossible, prohibited by law, or unsafe, reduce the speed of the motor vehicle to a reasonable and proper speed for the existing road and traffic conditions, which speed shall be less than the posted speed limit, and be prepared to stop.
  2.  The operator of a motor vehicle approaching a stationary towing or recovery vehicle, a stationary utility maintenance vehicle, a stationary municipal maintenance vehicle, or a stationary highway maintenance vehicle, that is displaying flashing yellow, amber, or red lights, shall approach the vehicle with due caution and shall proceed in one of the following manners, absent any other direction by a peace officer:
  a.  Make a lane change into a lane not adjacent to the towing, recovery, utility maintenance, municipal maintenance, or highway maintenance vehicle if possible in the existing safety and traffic conditions.
  b.  If a lane change under paragraph “a” would be impossible, prohibited by law, or unsafe, reduce the speed of the motor vehicle to a reasonable and proper speed for the existing road and traffic conditions, which speed shall be less than the posted speed limit, and be prepared to stop.
2002 Acts, ch 1013, §1; 2003 Acts, ch 2, §1
For applicable scheduled fines, see §805.8A, subsection 11 
Additional penalties for violations causing serious injury or death, see §321.482A