Bruce Webb and his father were driving a tractor manufactured by Navistar International Transportation Corp. (Navistar) at night on a public road. Webb was standing on the tractor’s draw bar and his father was driving. The tractor was equipped with flashing amber lights, a red taillight, and a reflective slow-moving-vehicle triangle. At the time of the accident, the amber lights and the taillight were not working, and Webb was blocking the view of the reflective triangle by standing on the tractor’s draw bar. Cautionary stickers on the tractor warned the operator not to allow another person to ride on the tractor unless a seat was provided. A car struck the tractor in the rear, seriously injuring Webb. Webb (plaintiff) brought a products liability claim against Navistar (defendant). The trial jury returned a verdict in Webb’s favor, and Navistar appealed, arguing that the evidence was insufficient to support a verdict, and that the jury should have been instructed that it could apportion liability between the parties.