transit

Transit refers to the movement of people or goods between locations. In urban planning, transit denotes public transportation systems that move people within cities and between regions. Common modes include buses, heavy and light rail, subways, trams, ferries, and commuter rail.

Transit systems are typically operated by government agencies or private consortia under public contracts. Funding combines fares, subsidies, and capital investment. Services are organized into networks with schedules, routes, and fare structures. Key performance indicators include frequency, coverage, reliability, travel speed, and accessibility.

Urban planning aims to improve transit through measures such as transit-oriented development, integrated fare systems, and enhanced accessibility. High-capacity, reliable services can reduce road congestion and emissions. Emerging concepts include bus rapid transit, light rail, autonomous transit, and on-demand microtransit, as well as innovations in signaling, energy efficiency, and last-mile connectivity.

In astronomy, transit describes the passage of a smaller body across the disk of a larger one as seen from an observer. Planetary transits cause characteristic dips in a star’s brightness and are used to determine sizes and orbital periods of planets, study planetary atmospheres, and detect exoplanets. Transits of stars by their planets also yield insights into stellar properties and planetary systems, contributing to methods such as transit photometry and transit timing variations.