A car horn sounds a short distance away. The driver pauses, looks around, momentarily distracted, and then tentatively reverses into the parking space. Ignition off. A moment’s pause while a form is filled. It’s good news. Her hands go up to her face out of sheer relief.

This young Asian woman has just passed her driving test in West Didsbury, Manchester. She climbs out of the car, hugs her instructor and, beaming, poses for a photograph holding her certificate, capturing one of the classic coming-of-age rituals.

Delighted as she is by her success, she might be surprised to learn that it has come against the odds. According to statistics obtained by the Guardian, unconscious bias appears to be putting some learners at a disadvantage because of their race.

The figures, revealed as part of the Guardian’s Bias in Britain series, show women and people of colour are significantly less likely than white men to pass UK practical driving tests. According to data from 2008-17 released by the Driver and Vehicle Standards Agency (DVSA) after a freedom of information request, black women had the lowest pass rates (32%), and white men the highest (56%). Overall, women had a pass rate of 43% and men 50%.

In an hour at the West Didsbury DVLA centre, you begin to see why that may be the case. Most of the test-takers are from minority backgrounds, but every examiner who will decide their fate today is a white, middle-aged man.

The DVSA says that it is vital that all drivers demonstrate they can drive safely and insists that the agency is committed to equality.

“All candidates are assessed to the same level and the result of their test is entirely dependent on their performance on the day,” Chief Driving Examiner Mark Winn said. “We constantly monitor our examiner’s performance so they conduct and assess driving tests in accordance with the standards set. This includes the supervision of live tests.”

But for Shazia Akkari, who has been running her driving school, Drive with Shazia, in Manchester and the surrounding areas for almost a decade, the statistics are upsetting but not entirely surprising.

Akkari, 36, who is of Pakistani descent, says she has advised her minority pupils not to go to a particular test centre because she believes one examiner treats her Asian and black students differently to their white counterparts.

She refuses to name the centre but says she complained and nothing happened, and the examiner remained in post. Now she makes a point of sitting in the back of the car when her students are taking their test, and she says she has seen things that have bolstered her suspicions that not every verdict is a fair one.

“I’d been teaching this Afghani student,” she remembers. “His English wasn’t very good and when he got into the car to take his test he explained this to the examiner. He then asked the examiner to put his seatbelt on. For some reason the examiner took a real issue with this. He responded in a way that I can only describe as aggressive. And then this aggressive tone continued all the way through the test.

“At the end of it, my student failed. I’d used the test centre before but I didn’t like what had just happened. We complained, it was investigated by the test centre manager but he denied it and nothing happened.

“There was another time with the same examiner. This time it was an Asian female student of mine. After the test she was in tears. It was his tone more than anything. She broke down.

“He was fine when I was in the car with white students. He was definitely different [with minority students]. The first time I just thought he was having a bad day, but then for it to happen more than once …”

She adds: “Taking a test is so nerve-wracking anyway. You don’t need this added pressure. He definitely spoke more harshly to people of a different colour. So now if I am teaching a person who is foreign, I tell them to stay away.”

Akkari, a former primary school teacher, has given driving lessons to thousands of people, some of them hailing from China, Nigeria, Jamaica, Afghanistan, India and Pakistan.

“It is upsetting. One person is not better than another simply because of the colour of their skin. It should be equal, there shouldn’t really be a difference,” she says.

“I never used to think there was a bias. If someone failed their test I always thought it was because they had done something wrong. Of those tests that I have sat in with, I would automatically know before the examiner if they had failed – but now that I think about it, maybe something else has always been at play.”