Tougher driving theory exams stumped nearly half of learner drivers at Worthing test centre, Driver and Vehicle Standards Agency (DVSA) figures show.
Pass rates are at a decade-long low nationwide after changes to exam questions last year, with fewer than half of would-be motorists getting the green light.
The AA called some of the questions obscure and said those sitting the test would need to study hard.
Worthing test centre conducted 4,873 theory tests between April 2018 and March this year, the most recent months where data was available; with 48 per cent of learners passing.
DVSA statistics reveal 47 per cent of learner drivers across Great Britain overcame the exam in the last 12 months, down a quarter in a decade.
The theory test, a standalone part of the driving test since 1997, has undergone reforms in recent years to make it harder.
They include upping the number of multiple-choice questions and stopping their publication in advance online, to prevent exam-takers from memorising answers.
Meanwhile, the hazard perception test, a video requiring learners to flag up dangers on the road, now simulates severe driving conditions such as snow and rain.
AA president Edmund King said: “There are lots of misconceptions about learning to drive.
“One of the most enduring is that you can pass the theory test with a bit of common sense and good luck. You can’t.
“Some of the questions are a little obscure and do not seem to reflect the reality of driving and perhaps need revisiting to ensure they are relevant to drivers.
“The one that caught me out was the blue sign with a 30 and a red line through it denoting the end of a minimum speed limit area which I have never encountered in 40 years of driving.”
Across Great Britain, more than 1.3 million theory tests were conducted over the 12-month period.
Women performed strongest – 49 per cent went on to pass compared to 46 per cent of men.
At Worthing test centre, 51 per cent of female applicants came through, as well as 46 per cent of their male counterparts.
Bodmin test centre, in Cornwall, had the lowest pass rate of any test centre, with only a third of 28 applicants successful.
Isle of Barra test centre, in the Outer Hebrides, by contrast, had the highest pass rate: 67 per cent – double that of Bodmin.
Mark Winn, chief driving examiner for the DVSA, said: “It’s essential that all drivers demonstrate they have the right skills, knowledge and attitude to drive safely.”
• Report by Alex Shaw, data reporter