The "Blue Line" typically refers to a specific route or service in public transportation systems, particularly in cities like Chicago and Los Angeles. In Chicago, the Blue Line is part of the Chicago Transit Authority (CTA) and connects the O'Hare International Airport to downtown, making it a vital link for commuters and travelers. In addition to public transit, "Blue Line" can also refer to the thin blue line, a symbol representing law enforcement and their role in maintaining order. This symbol is often used to honor fallen police officers and to signify support for police forces across various communities.