Learner drivers taking tests when they resume today are under extra pressure to pass as a backlog means it could be several months before they get another chance.
More than 450,000 tests have been cancelled due to the coronavirus pandemic, according to Driver and Vehicle Standards Agency (DVSA) figures.
Tests have been suspended since early January, but restart in England and Wales today.
Those who fail their test in Britain face an average waiting time of 17 weeks to book a new slot.
Jade Bone, 24, is taking a test in Southampton on Thursday and is concerned at the consequences of not passing.
“It’s going to be so long before I’m able to get another test if this one doesn’t go quite to plan,” she told the PA news agency.
“That’s quite frustrating and a scary prospect, especially because it’s an expensive thing to do, having lessons.”
Ms Bone’s instructor, Rob Fenn, of RED Driving School, said tests are “essentially fully booked” due to pent-up demand.
He is advising eager students to “sit at a computer and keep refreshing the page”.
AA Driving School pupil Jack Hayes, 25, who is taking a test in Cardiff on Thursday, admitted he “really panicked” when it was announced that driving lessons would only resume last week.
He said: “I booked (the test) back in October thinking there was plenty of time to learn before then.
“I feel lucky to be one of the first people given the chance to take it, but I’ve had much less time to practise and prepare with my instructor.
“There is also more pressure to actually pass than normal because the waiting list is so long before I can try to retake it, and more money would have to be spent on lessons to stay test-ready.”
The DVSA said it is offering an additional 2,500 car tests per month by utilising weekends and bank holidays.
Up to 300 new examiners are also being recruited to help reduce the backlog.
Only 46% of tests in the year to March 2020 were passed, leading the DVSA to urge candidates they should be “properly prepared”.
The most common reasons for failing include not looking properly at a junction (22%), not using mirrors correctly when changing lane or direction (17%), and not moving off safely (8%).
DVSA chief driving examiner Mark Winn said: “Learners should only take their driving test if they are completely ready to pass, and feel they’ve had sufficient practice driving on a variety of roads and in different conditions.
“Thousands of people fail their test every year because of common errors which are potentially dangerous and avoidable.”
Tests can be rescheduled free of charge if learners feel they need more time to prepare.
Recent analysis by PA found that driving licence numbers among young people have fallen to the lowest level since current records began.
Just 2.97 million people in Britain aged 16-25 hold a full licence, down from 3.32 million in March 2020.
Motoring experts said the decline was due to the suspension of lessons and tests.
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