Iowa Code § 321.333: Duty of drivers.

Any driver of a vehicle or operator of a motor-driven vehicle who approaches or comes in contact with a person wholly or partially blind carrying a cane or walking stick white in color or white tipped with red, or being led by a guide dog wearing a harness and walking on either side of or slightly in front of said blind person, shall immediately come to a complete stop, and take such precautions as may be necessary to avoid accident or injury to the person carrying a cane or walking stick white in color or white tipped with red or being led by a guide dog.