Subheading 853010 covers apparatus specifically designed for railways and subways — including track circuits, interlocking systems, and platform signals. Subheading 853080 captures equipment for roads, inland waterways, ports, and airfields. The determining factor is the mode of transport the equipment is engineered to serve, not its general electronic function.

Parts specifically designed for the signaling and safety apparatus of this heading classify under 853090. However, generic electrical components (such as switches or connectors) that are not dedicated to traffic control equipment may classify in the switching and protection apparatus headings rather than here. A binding ruling is advisable for multipurpose components.