Iowa Code § 321.288 : TRANSPORTATION — VEHICLES — Motor vehicles and law of the road —SPEED RESTRICTIONS — Control of vehicle - reduced speed
1. A person operating a motor vehicle shall have the vehicle under control at all times.
2. A person operating a motor vehicle 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 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 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 or alternative reflective device as provided by section
321.383.
f. When approaching and passing through a road work zone.