Athens Mass Transit System

The Athens Mass Transit System is the largest mass transit system of Greece. The system is run by the OASA S.A. organisation and serves Athens Urban Area and the Athens Metropolitan Area (whole of the Region of Attica without the island section).
Companies.
In March 2011, with the Greek Government Law 3920 Attiko Metro Operational Company (AMEL S.A.) absorbed Athens-Piraeus Electric Railways S.A. and TRAM S.A. and was renamed "STASY S.A." (). Also ETHEL S.A. absorbed ILPAP S.A. and was renamed as "OSY S.A." (). The mergers were officially announced on June 10, 2011.  While mergers at the top management level took place quickly, integration of the former companies at operations and support level proceeds slowly.
As of July 2011, the Athens Mass Transit System consists of:
TRAINOSE S.A. ()
OSY and STASY is wholly owned by OASA. TrainOSE (for its Proastiakos department) is coordinated by Athens Urban Transport Organisation (Organismos Astikon Syngoinonion Athinon - OASA, ), a state-owned company. 
ISAP, ETHEL and ILPAP were wholly owned by OASA S.A.. AMEL and Tram S.A. until June 2011 were subsidiaries of Attiko Metro S.A. (), a company that is currently wholly owned by the Greek government.
TrainOSE S.A., which absorbed the former Proastiakos S.A. in 2007, became independent of the OSE group in 2008 and is now a separate private company.
OASA regularly conducts street photography and videography competitions both in black-and-white and in colour for photos taken while inside its means of transport.