Susan Parks v. Ariens Company, 829 F.3d 655

Timothy Parks died when a Gravely Promaster 152Z riding mower he owned rolled over him on an embankment; his widow, Susan Parks, sued the manufacturer, Ariens Company, for negligent failure to equip the mower with rollover protection (ROPS).
The 152Z was sold new without ROPS as an optional add-on; Ariens offered ROPS for slope operation.
The dealer (Robertson Implement) who sold the mower to Parks’ predecessor testified his routine practice was to inform customers about ROPS and to have customers sign an Equipment Safety Check that asks whether ROPS was in place or rejected, but no signed form from Parks’ sale survived.
The district court granted summary judgment for Ariens, holding that offering ROPS as an optional feature satisfied the manufacturer’s duty; Parks appealed.
The Eighth Circuit adopted the optional-equipment doctrine under Iowa law, found undisputed evidence that Parks was likely informed and was in a position to make the risk/benefit choice, and held Ariens fulfilled its duty by offering ROPS as optional.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether a manufacturer can satisfy its duty by offering optional safety equipment that would have prevented the injury	Parks: Ariens was negligent for not including ROPS on every 152Z; optional offering is insufficient	Ariens: Offering ROPS and informing buyers satisfies manufacturer’s duty when buyer can make an informed choice	Court: Adopted optional equipment doctrine; Ariens satisfied its duty by offering ROPS and providing information
Whether Parks was sufficiently informed and able to assess risk	Parks: Dealer did not prove he informed Timothy Parks about ROPS	Ariens: Dealer’s regular practice and checklist show Parks was likely informed and able to decide	Court: Evidence showed dealer’s standard practice and checklist likely informed Parks; requirement met
Whether the 152Z is unreasonably dangerous without ROPS for normal uses	Parks: 152Z is unreasonably dangerous without ROPS (single-use argument)	Ariens: 152Z can be used safely on level ground without ROPS; multiple uses exist	Court: Found normal, non-dangerous uses (e.g., level-ground mowing); requirement met

Biss v. Tenneco, Inc., 409 N.Y.S.2d 874 (N.Y. App. Div. 1978) (formative decision recognizing that making safety equipment available as an option can relieve manufacturer liability)
Wagner v. Int’l Harvester Co., 611 F.2d 224 (8th Cir. 1979) (endorsing Biss theory under Minnesota law)
Scarangella v. Thomas Built Buses, Inc., 717 N.E.2d 679 (N.Y. 1999) (articulating three-part test for optional equipment doctrine)
Bilotta v. Kelley Co., 346 N.W.2d 616 (Minn. 1984) (narrower formulation requiring optional equipment to impair some uses)
Wright v. Brooke Group Ltd., 652 N.W.2d 159 (Iowa 2002) (Iowa adoption of Restatement (Third) § 2(b) on design defect)