A woman is in a serious condition after a collision on Mary Street in Dublin city centre.
An accident involving two cars and a pedestrian on the Red Luas line also means services are disrupted.
The Gardaí have asked trams not to run between Smithfield and the city due to the incident.
The company has said services are running between Saggart -Tallaght and Smithfield, and that Luas tickets are valid on Dublin Bus for the duration of the disruption.