Almost 239,000 ambulances spent over half an hour at a hospital last year, before offloading a patient and getting back on the road.
It represents four out of every five ambulances that arrived at emergency departments.
Turnaround times involve the interval between an ambulance's arrival at a hospital to when the crew has handed over a patient and is ready to take another call.
The HSE's target time is less than 30 minutes.
However, that aim was only met in 20.8 per cent of cases last year.
The worst last year was Cork University Hospital, where the target was only met in 4.5 per cent of cases.
That was followed by Mercy University Hospital in Cork, at 5.5 per cent.
The target was met in less than 10 per cent of cases in five other hospitals.