The Automobile Association has confirmed that European Car Free Day turned out to be the busiest day of the month so far on Dublin's roads.
Spokesman Conor Faughnan said it was ironic that bad weather conditions had resulted in a heavier traffic flow.
Ireland took part in the annual event for the fifth year. Over 1,000 European towns and cities, including 20 in Ireland, participated.
People were encouraged to explore alternative forms of transport with work colleagues and school children urged to avail of car pooling, cycling, public transport options and walking to work or school.
Many countries throughout Europe offered bus and commuter train transport for free in the hope of encouraging drivers out from behind the steering wheel.
Dublin Bus gave away 20,000 free prepaid tickets in advance. Free Bus Éireann services were also available in Cork, Galway, Limerick and Waterford.
Neither Rome nor Berlin took part this year and street closures in Paris were scaled back to largely token levels because of huge traffic jams in 2003.