Onibus

Onibus, or ônibus in Brazilian Portuguese, is a road vehicle used to transport multiple passengers. The term is widely used in Portuguese-speaking countries, while other regions may use autocarro or autobus. Buses operate in urban, suburban, and intercity settings and can be owned by public transit agencies or private companies. They are a key component of public transport networks and are often integrated with other modes such as trains, trams, and metro systems.

Historically, buses evolved from horse-drawn omnibuses in the 19th century. Motorized buses emerged in the late 19th and early 20th centuries and expanded rapidly with urbanization, enabling mass mobility and influencing city planning and development.

Modern buses come in several configurations. Single-deck and double-deck designs serve different capacity needs, while articulated and bi-articulated buses provide higher capacity for dense urban corridors. Typical lengths range from about 6 to 18 meters. Propulsion has traditionally been diesel, but natural gas, electric, hybrid, hydrogen, and trolleybus variants are increasingly common. Battery-electric buses and other zero-emission options are expanding as cities seek to reduce air pollution and greenhouse gas emissions.

Operations and infrastructure include urban route networks, trunk corridors, and intercity services. Many cities deploy bus rapid transit (BRT) systems with dedicated lanes, priority at signals, and efficient stations to improve speed and reliability. Fare collection has evolved from cash to contactless payments and smart cards, while accessibility features such as low-floor boarding, kneeling suspension, and wheelchair ramps are widely implemented.

Environmental and social aspects focus on efficiency, emissions, and access. Buses offer relatively low emissions per passenger when well utilized and can provide mobility for populations with limited alternatives, making them central to inclusive urban transportation planning.