Half of cars on average that were brought for their NCT in the Shannonside region passed the test in the first seven months of this year.
Updated figures from the NTA show the average pass rate at 51 percent at the NCT centres in Longford, Castlrea, Carrick , Ballinalsoe and Athlone.
66,700 vehicles were brought for their NCT exam between January and July of this year in the region's 5 centres.
43,404 of these passed the examination locally, while a further 23,296 failed and required a re-test.
Ballinasloe recorded the highest local pass rate so far this year at 58 percent, with 35 percent failing and 5 percent recorded as dangerous fails.
The pass rate at the Athlone test centre was the next highest at 55 percent, with 6 percent of all tests recording a dangerous result.
Longford had a failure rate of just under half, with 7,844 passes out of 12,010 tests.
Meanwhile in Carrick on Shannon, 48 percent of vehicles passed the test in the first 7 months of the year.
While Castlerea NCT centre recorded one of the highest failure rates in the country at 48 percent.