A Line

A Line or A-line may refer to:

Transport

 * A (New York City Subway service), rapid transit line
 * A Line (Los Angeles Metro), a light rail line in Los Angeles County, California
 * A Line (RTD), commuter rail line between Denver and Aurora, Colorado
 * Atlantic Coast Line Railroad, rail line in Florida
 * Metro A Line (Minnesota), a bus rapid transit line in Minneapolis, Saint Paul, and Roseville, Minnesota
 * A-Line (Hamilton), planned rapid transit line in Hamilton, Ontario, Canada
 * RapidRide A Line, bus route in King County, Washington
 * Line A (Buenos Aires Underground), Argentina
 * RER A, commuter rail line in Paris, France
 * A (Los Angeles Railway), former streetcar service

Other uses

 * A-line (clothing), a style of skirt or dress
 * Arterial line, a thin catheter inserted into an artery
 * A-line - a finding in medical ultrasound of the lung