A lift truck includes a frame, a pair of laterally spaced apart outriggers extending from the frame, and a load handling assembly secured to the frame adjacent to the outriggers. The load handling assembly includes a mast assembly positioned between the outriggers and a carriage assembly including fork structure for supporting a load on the load handling assembly. The carriage assembly is movable vertically along the mast assembly and laterally with respect to the mast assembly. Optical sensor structure of the truck monitors for conditions wherein movement of the carriage assembly would result in contact between the load and the outrigger(s). A vehicle controller receives a signal from the optical sensor structure and prevents movement of the carriage assembly toward the outrigger(s) if the signal from the optical sensor structure indicates that such movement would result in contact between the load and the outrigger(s).