Tight security measures go into force in Athens for 48 hours from tomorrow afternoon for the European Union summit, during which the crucial EU enlargement treaty is to be signed. The city center will be blocked off completely to traffic, and the police have asked the public to keep their trips to the absolute minimum and to choose alternative routes wherever possible. – Traffic restrictions will affect arterial roads leading from the airport to hotels as of Tuesday afternoon, when the 41 European leaders and dignitaries attending the meeting start arriving. – Strict security measures will be imposed at all hotels where the visitors are staying. – On Wednesday and Thursday, from early morning until at least 9 p.m., access to downtown Athens will be next to impossible, as a smaller version of the Athens restricted traffic ring is implemented. – The area surrounding the Zappeio and much of Plaka near the Stoa of Attalos will be strictly out of bounds to vehicles, and some 11,000 police officers will be on duty to enforce the measures. – Public transport will also be affected, with timetables and routes continually changing. Passengers can find out about the ongoing changes by listening to the radio. The police will be issuing regularly updated bulletins to radio stations. – Some demonstrations are expected to start out from Syntagma Square. No ban has been announced on demonstrators moving toward any embassies, but any demonstrators who attempt to break out of the inner circle will face police. A police spokeman said the police would not seek conflict, but they expect the organizers of any demonstrations to behave responsibly. Authorities see the security and traffic restriction measures as a dress rehearsal for the 2004 Olympics.