Forklifts are highly maneuverable, narrow machines that can overturn when operated at high speeds, driven around tight turns, and over uneven surfaces, or when elevated loads become unbalanced [Janicak and Deal, 1999; Collins et al., 1999a; Lifschultz and Donoghue, 1994; Horberry et al., 2004]. Forklifts pose additional hazards for pedestrian workers [Born et al., 1996; Stout-Wiegand, 1987], particularly in manufacturing, freight handling, and warehousing settings with narrow aisles where pedestrian workers and forklifts share travel space [Collins et al., 1999a; Horberry et al., 2004; Larsson and Rechnitzer, 1994].