The N24 road eastbound between Clonmel and Carrick-on-Suir remains closed following an accident.
A pedestrian was seriously injured in the incident and has been taken to South Tipperary General Hospital in Clonmel.
The man in his 20s suffered serious head injuries.
The incident happened at Deerpark, near Carrick-on-Suir.
It is expected that the road will remain closed until about midday.
Diversions are in place from Kilsheelan.