Olympic spectators face a two-hour wait to get through security checks, Athens organisers have revealed.
Visitors to the opening and closing ceremonies have also been told to turn up at Athens' main Olympic stadium three hours in advance.
"Waiting times are comparable to those in airports," said organising committee executive director Marton Simitsek.
Organisers are also pleading with the five million Athenians to leave their cars at home to prevent gridlock.
They unveiled an ambitious policy designed to increase the number of people using public transport from 33 percent to 50 or even 75 percent.
No car parks inside the 35 sports complexes
No-access "red zones" around venues
Drive-through-only "yellow zones" stretching up to 1km from every venue
Special Olympic lanes reserved for official cars, buses and minivans
All ticket holders, volunteers and Games personnel will be allowed to use public transport for free on their way to venues
An Olympic taxi centre with 7,000 accredited cabs will
also be available to drop off and pick up spectators from
"We want the Olympic community to move around the city safely and quickly and we want visitors, mainly foreigners who don't know the city, to have easy access to all Olympic venues," Greek Transport Minister Michalis Liapis said.
About 1.5m tourists are expected to visit Athens
during the Olympics, adding to the capital's nearly five
million residents and two million cars.
In Athens, unlike other European cities, taking public transport to big events such as a football match or concert is rare.
* About 1.9m out of a total 5.2 million tickets have been sold so far.