The introduction of a computer based theory test for the learner driver's licence has led to a dramatic fall in the pass rate.
Of the 20,000 tests taken under the new system in the past three months, only 42% were passed.
Under the former scratch test method, the pass rate was 77%.
Both systems ask multiple choice questions based on the road code.
The Transport Agency says the drop was expected, as the question selection is now truly random.
It predicts the pass rate will improve over time as people become aware of the nature of the test, and the need to better prepare for it.
The agency says the harder computer based test will ultimately lead to better drivers.