Over 20,000 cars failed the NCT in the Shannonside region in the first nine months of this year.
The statistics were made available on the official NCT website.
Just over 37,000 tests were carried out in Carrick-on-Shannon, Castlerea and Longford between January and September.
Castlerea had the highest pass rate in the region at 45.61%.
That was followed by Carrick-on-Shannon at 45.05% and Longford at 42.17%.
Across all three centres there were over 17,400 failures with over 3,000 of those dangerous failures.
Carrick-on-Shannon recorded the highest amount of those at 1,146.