In maritime navigation, one prolonged (long) blast followed by two short blasts is a vital signal used in restricted visibility (like fog) to identify a vessel that is "maneuvering with difficulty" or restricted in its ability to maneuver. This specific sound signal tells other nearby captains that the vessel may have the "right of way" because it cannot easily change course. This includes sailing vessels, fishing vessels engaged in trawling, vessels not under command, or vessels engaged in towing. It is effectively a "stay clear" warning. In the context of railroads, a similar signal (one long, two short) was historically used by engineers to signal a "meeting point" or to warn of an approaching train on a single track, though modern radio communication has largely replaced this in 2026. On the water, however, these sound signals remain a primary safety requirement under the International Regulations for Preventing Collisions at Sea (COLREGs), ensuring that even if radar fails, ships can communicate their status to prevent collisions in thick fog or heavy rain.