Only Cork and Dundalk have formally declared their intention to take part in the Republic's "car-free day" today.
Officially designated "In Town Without my Car" the day is the high point of European Mobility Week which has been running since last Friday.
In Cork, the city council will close some city streets to all vehicles other than those on which public transport runs.
Cork City Council will close off most of the city centre to traffic from 11am to 5pm with thoroughfares such as Patrick Street, Academy Street, Half Moon Street, Emmet Place, Faulkner's Lane, Bowling Green Street, Drawbridge Street and Paul Street closed to cars.
Oliver Plunkett Street, Princes Street, Cook Street, Pembroke Street, Marlborough Street, Beasley Street, Robert Street, Morgan Street and Caroline Street will also become car-free zones between 11am and 5pm.
There will also be an organised cycle around the city and free park and ride services. The city council and private companies are also promoting car pooling.
Although officially taking part, Dundalk will not be closing streets. The town council will provide bicycle lock-up facilities in the town centre and in all council buildings. It is also working with local schools and employers to encourage staff and pupils to cycle, car share or walk rather than use cars.
The failure of Dublin City Council to take part in the car-free day, although the city is participating in European Mobility Week, was criticised by Minister of State for Transport Ivor Callely who said it was inexplicable.
A spokesman said the closure of streets in previous years had been criticised by commuters who felt it caused further congestion. However, the council will promote car pooling on main roads into the city - a registration point will be set up at Clontarf Road and cars with three or more people will enter a free draw for €1,000. Walking and cycling is to be encouraged all week and schools will visit local parks to tour, explore and find out more about nature in their local area.
There will also be historic tours of the city and bikes will be available for hire in the central area. Throughout the week, free buses will circulate around large shopping centres.
Bus Éireann services in Cork, Limerick, Galway and Waterford will be free of charge between 10am and 4pm and town services in Sligo, Dundalk and Drogheda will be free all day.
Information about switching to public transport in Dublin can be obtained at the Travel Advice Centre at the junction of Grafton Street and South King Street.