Food bloggers who are fans of Subway's chopped salads are a reliable source of information about the salad chopper tool Subway uses. Subway.com features no details about specific utensils its employees use in their stores.
Subway is a franchise, so the exact salad choppers employees use may differ from store to store. The consensus among food bloggers who frequent Subway is that company uses a mezzaluna or some pizza-cutter-shaped variation as a salad chopper. A mezzaluna, or half-moon, is a double-blade Italian culinary instrument, typically used for chopping large quantities of fresh herbs. A variation manufactured by OXO resembles a double pizza blade.