public transportation; public transport
Refers to shared passenger transport services such as trains, buses, and subways, typically operated by public or private entities for general use.
This city has well-developed public transportation.
Let's use public transport for the environment.
交通機関 is a broader term for any transportation facility or system, including private cars and freight, while 公共交通機関 specifically means public transport.
Compound of 公共 (public) + 交通 (traffic/transportation) + 機関 (facility/organ). The term is a modern coinage reflecting the concept of public transit systems.