More than half of all cars submitted for an NCT failed the test on initial inspection last year, according to the Road Safety Authority.
Figures show 51% of more than 1.35m cars had to return for a second inspection in 2017.
Despite the fact that a majority of vehicles failed the test last year (over 688,500 cars), the pass rate of 49% was the highest level since 2011 — the last year that a majority of cars passed the NCT. Most cars successfully obtained their NCT certificate on the second inspection in 2017, with a pass rate of 91.3% in re-tests.
An analysis of the performance of almost 50 well-known car brands reveals Dacia cars had the stand-out performance with 76% of vehicles passing the NCT on first inspection — way ahead of any competitor.
The good results are largely explained by the fact that Dacia cars were comparatively newer than any other make tested, with an average year of manufacture of 2013 for the Romanian car maker. The average year of manufacture of all vehicles submitted for the NCT last year was 2003.
In general, the results show the older a vehicle, the more likely it is to fail the test. For example, 85% of 2015-reg cars passed the test, but the pass rate fell to 61.2% for 2010 models and 32.8% for those registered in 2000.
However, there are exceptions including the worst performer, Korean car manufacturer Ssyangyong, whose vehicles had an average pass rate of 23.6%, despite having the second youngest age profile of all leading brands, with an average year of manufacture of 2010.
Similarly, 50 Rolls-Royce cars which had an average age of 37 years performed better than many leading modern car makes, with an average pass rate of 46%. A Rolls Royce registered in 1932 — the oldest vehicle submitted for an NCT last year — passed the test.
After Dacia, other popular car makes with a comparatively high pass rate included Lexus (58.7%), Kia (58.3%), Skoda (54.8%), and Toyota (53%).
Several luxury, high-performance models also performed well such as Lamborghini and Porsche, which scored pass rates in excess of 58%, while Ferrari — despite having an average vehicle age of 17 years — obtained an average pass rate of 57%.
Leading brands with below-average pass rates included Chevrolet (36.2%), Alfa Romeo (40.4%), Renault (41.5%), and Fiat (42.9%).
The five most common components of a vehicle which caused a car to fail the NCT last year were lamps, followed by suspension and steering, brakes, tyres, and bodywork.
The most common problem with most cars related to issues with “lighting and electrical”, but brakes were the most frequent fault with Daewoo and Rolls Royce and “steering and suspension” with Alfa Romeo, BMW, Saab, Mercedes, and Opel.
“Vehicle and safety equipment” was the most common fault with a number of makes, including Dacia and Ferrari, while the most regular issue with Audi was “wheels and tyres”.
The total number of cars tested last year fell by 7.5% compared to the previous year, with over 110,000 fewer vehicles submitted.
The overall number of tests has been falling in recent years — down from 2.26m in 2015 to 2.04m last year.
The highest pass rate in the country was at Kilkenny NCT test centre, where 56.6% of vehicles passed.
The lowest pass rate, by some distance, was at the Monaghan centre, at 37.5%.