John Quinn was diagnosed with younger onset dementia at the age of 59, but his partner had noticed years earlier there were issues with his driving.

Glenys Petrie said John started vocalising the driving process, as he sat behind the steering wheel.

"He would stop in the middle of the motorway and there'd be no traffic there and I'd say: what's going on? And he'd say: I have to give way to the right," Ms Petrie said.

"We had too many close calls to the point where I refused to be a passenger in the car, I said 'If we need to go somewhere, I'll be driving'."

After his dementia diagnosis, Mr Quinn followed Queensland rules and informed the Department of Transport about his medical condition.

"I started to have enough insight to realise that things were becoming a little more difficult and at that point my GP started to insist that I go for a test, a driving test," he said.

The now 71-year-old paid to do a full assessment and practical test with a driving instructor and an occupational therapist.

He passed and was allowed to keep driving with conditions, but ultimately decided to hang up his car keys.

"In the end I thought to myself, well, I don't drive much anyhow, so what's the sense in continuing to drive?

"So, we went down to the Department of Transport and I surrendered my driver licence," he said.

The former school principal and dementia awareness advocate said he was OK with the decision because there was a "lead-in" period.

He bought a bicycle and a new chapter began.

"I'd sometimes ride my bike over to a friend's place and then together we'd get in his car and we'd drive over to Chandler where we'd go swimming," he said.

But Ms Petrie said for some people living with dementia the process is more abrupt.

"They were truck drivers or drivers and so in one day they lost their career, their ability to pay their mortgage.

"It's a complex issue — driving is a complex task and dementia is a complex issue, but everyone needs to be treated individually and respectfully."

Video safety test being developed

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University of Queensland psychology researcher Dr Theresa Scott said people living with dementia will be safe to drive at first.

"But they'll get to the stage where their physical and cognitive capacities will decline to such a stage that they're no longer safe," she said.

Finding the right time to stop driving can be fraught with emotion for families and doctors required to assess an individual's medical fitness to drive.

"If someone is told that they can't drive while they are potentially still safe to drive, that has a significant impact on people's emotional responses," Dr Scott said.

According to estimates from the Australian Institute of Health and Welfare and Dementia Australia, there are between 386,000 and 487,500 Australians living with dementia.

Dr Scott said there is currently no clear process to determine when driving is deemed unsafe and that can put GPs in the "very difficult" role of having to "police driver safety" with their patients.

Her team is developing video-based hazard perception tests that can be used to aid assessments.

"What the test aims to do is to test that person's ability to predict a traffic incident, so to predict a hazard for example," she said.

Dr Scott said sometimes individuals with a dementia diagnosis are not tested at all, or are given a pen and paper memory test, before having their licence revoked.

She said the new video-based assessments will be fairer and more objective.

"It means that people can continue to drive while they're safe, they can be tested by their GP and their GP will feel confident to say if they can continue to drive."

And it is hoped people living with dementia will better accept the results.

"Accepting that decision from your health professional to stop driving is very important in them moving forward and finding other ways to get to their community," Dr Scott said.

Maintaining dignity among drivers

The test is being fine-tuned alongside people living with dementia and will incorporate real on-road footage that individuals view and respond to.

Dr Scott said it could also have wider applications.

"We say that driving safety should look the same no matter what your age or condition so … the test would be certainly suitable for older people as well," she said.