A harder driving test has been introduced amid concerns that drivers are merely memorising the answers to pre-published questions.
A survey carried out by the AA on more than 11,000 drivers found significant lapses in knowledge about basic driving theory.
The survey, conducted by Populus, revealed that more than 25 per cent of respondents did not know that a broken traffic light meant that no driver had priority at a junction.
When faced by an amber flashing light at a pelican crossing, 18 per cent of respondents answered that they would have to stop and wait for a green or red light.
The corrrect answer, that the flashing light means a driver must give way to pedestrians on a crossing, was chosen by just over half of respondents.
Throughout the survey it was found that younger drivers performed better than older drivers.
"Knowing the theoretical rules of the road is important for drivers," said Mark Peacock, head of AA Driving School.
"It's encouraging that young drivers did better in the poll questions than older [people] - perhaps a sign that those who have recently taken a theory test have a better understanding of driving theory than those who took it a few years ago.
"Learners should not unduly worry about the changes to the test. The new test calls for greater understanding, which can be gained from professional tuition and some time spent revising; both of which could have been needed to pass the theory test confidently before the changes."
The changes to the theory test will see the answers no longer published.