routenumber

A route number is an identifying label assigned to a specific transportation path within a network. It is used across road, rail, air, and public transit systems to distinguish one route from another and to aid navigation, administration, and maintenance.

In road networks, numbers convey hierarchy and geography. National systems often distinguish primary routes from secondary ones, and different countries use different formats. For example, the United States assigns Interstate numbers (I-5), U.S. routes (US-66), and state or provincial routes (such as SR-92). The United Kingdom uses categories like M for motorways and A or B roads. In Europe, the international E-road network overlays national routes with E-numbers that span multiple countries.

Public transit and rail also rely on route numbers or designations to identify services and lines. Bus, tram, and ferry services frequently use numeric or alphanumeric route identifiers. Rail networks use line numbers or service designations to mark specific corridors or branches. In aviation, route numbering appears in airways and flight plans, providing a systematic way to chart and manage air travel.

Signage and digital systems display route numbers on signs, maps, timetables, and in navigation apps. These numbers are usually assigned or revised by transportation authorities and can change when routes are restructured, extended, or decommissioned. Across regions, route numbers thus serve as concise references that coordinate wayfinding, infrastructure planning, and policy implementation.