The Greek army has been deployed at six locations on the Attiki Odos to help cars stuck on the highway after stalled cars and truck accidents created massive traffic jams, said government sources on Monday evening.
The drivers have been stranded since midday, during the 'Elpis' snowstorm that is expected to continue to Tuesday, unable to move to exits.
Key branches of the civil service as well as food stores, petrol stations and pharmacies will stay open.
"We ask citizens to avoid leaving their homes. It will be a difficult night," Climate Change and Civil Protection Minister Christos Stylianides said.
"The height of the snow is unprecedented in some areas."
Power cuts occurred in parts of Athens and nearby areas as well as the island of Evia, knocking out heating systems.
Heavy snowfall is rare in Athens but the city has now been hit by snowstorms for a second consecutive year.
Fifteen passengers were injured when a rail transport vehicle tried to pull a train carrying about 200 passengers which had halted in heavy snow in central Greece.
Two of the injured were in serious condition, a police official said.
Meanwhile, the Athens Municipality said that cars in Athens must use snow chains because of the continuing snowfall, cautioning drivers to keep movement to the absolute minimum.
It also said that efforts are focusing in keeping central roads open and ensuring access to the hospitals of Athens.
In Athens, train and metro station sections have been shut down due to weather conditions with Metro Line 1 (the electric train, or ISAP), will stop and start from the Irini stop, said Urban Rail Transport (STASY).
The Piraeus-Kifissia section between Irini and Kifissia was shut down to the end of the shift, STASY said.
Also, tram Line 7 (running between Asklipiio Voulas and Akti Possidonos stops) was temporarily ending at the Paleo Dimarchio stop in Glyfada until a fallen tree at the Kolimvitirio was removed.
Tram Line 6, which runs between Pikrodafni and Syntagma Square stops, is temporarily ending/starting at Leoforos Vouliagmenis stop.
Metro lines 2 and 3 are running as per usual, but stop at Doukissis Plakentias station instead going on to the Athens International Airport.
Transportation has been affected by a severe snowstorm that is expected to continue to midday today, Tuesday.