Attiki Odos (Greek: Αττική Οδός) is a privately owned toll motorway system in Greece. The Attiki Odos motorways form the outer beltways of the Greater Athens metropolitan area. The total length of the motorways is 65 kilometres (40 mi). The Attiki Odos system consists of the following motorways:
- A6: Eleusis - Athens International Airport
- A61: Markopoulo - Lavrio (planned)
- A62: Koropi - Athens International Airport
- A63: Ilioupoli - Paiania (planned)
- A64 (Ymittos Ring): Katechaki Avenue - Pallini (extension planned)
- A65 (Aigaleo Ring): Aspropyrgos industrial area - Ano Liosia
- A642: Doukissis Plakentias Avenue - Agia Paraskevi
Construction of the A6 motorway began in 1996. Part of it was opened along with the Eleftherios Venizelos International Airport to which it connects, in 2001.
In early 2003, the A6 was opened from Kifisias Avenue Interchange to Eleftherios Venizelos Airport; the Ymittos Ring was almost paved by this time, and tunnels were already complete. On 3 September 2003, the Ymittos Ring opened. This part of the motorway runs in the northern part of the Hymettus hills and became the road to bypass Mesogeion Avenue and link to Kifissou Avenue and its suburbs, and the Airport along with the eastern suburbs of Athens.
In November 2003, the western part opened from the junction with Motorway 8 to Kifisias Avenue. In April 2004, a small 2.5 km part opened, connecting the Ymittos Ring to the westbound direction of the A6.
Attiki Odos is considered one of the safest motorways in Europe. It was designed under strict safety-related technical specifications, including updated hard shoulders in either direction and high quality skid-resistant asphalt pavement, dense lighting and fencing. Attiki Odos features hundreds of CCTV cameras connected to the Traffic Management Centre (TMC), which detects any incidents occurring on the motorway and informs the intervention and maintenance patrol units to provide assistance. Other sophisticated safety systems include:
- Road pavement sensors
- Carbon monoxide measurement systems installed in tunnels
- TETRA system for communication with the patrol units
- Electronic variable message signs
- Automatic tunnel ventilation systems
Toll stations are located at the interchanges leading to the Attiki Odos motorway and the toll fare is paid when entering the motorway. The fare is the same regardless of the length of journey but depends on vehicle category. Drivers can pay either by cash, e-pass or a special account card; for motorbikes and cars the standard toll fares are 1.40€ and 2.80€ respectively.
On October 21, 2005 a new expansion plan was proposed. 76 km of motorway will be constructed, bringing the total length to 141 km. Extensions will be constructed towards Rafina, Lavrio and Vouliagmeni. The Hymettus Beltway will also be extended southwards to Vouliagmeni. Construction is estimated to start in 2009, as the final plans were announced to be complete in late May 2008.