A person operating a motor vehicle shall have the vehicle under control at all times and shall reduce the speed to a reasonable and proper rate:
   A.   When approaching and passing a person walking in the traveled portion of the public highway.
   B.   When approaching and passing an animal which is being led, ridden, or driven upon a public highway.
   C.   When approaching and traversing a crossing or intersection of public highways, or a bridge, sharp turn, curve, or steep descent, in a public highway.
   D.   When approaching and passing an emergency warning device displayed in accordance with rules adopted under Iowa Code section 321.449, or an emergency vehicle displaying a revolving or flashing light.
   E.   When approaching and passing a slow moving vehicle displaying a reflective device as provided by Iowa Code section 321.383.
   F.   When approaching and passing through a signposted construction or maintenance zone upon the public highway. (2008 Code § 17-288)