More than a million older drivers are risking a £1,000 fine by failing to disclose serious medical conditions.
It's compulsory to inform the DVLA if you have certain medical conditions, including visual impairments, diabetes, heart conditions or epilepsy.
But while almost one in three drivers over the age of 65 has one of these conditions, almost half of these have failed to notify the DVLA. Most - 57% - of drivers in this position say they haven't done it because they don't feel their condition affects their driving; one in eight say they didn't know they were supposed to, and around a quarter cite 'other' reasons.
"Regardless of age, drivers that have a notifiable or worsening medical condition or disability must disclose this to the DVLA and also to their insurer to stay within the law," says Gus Park, director of motor at Direct Line, which carried out the research.
"Even those who feel their physical status won't affect their driving must still disclose their condition, as failing to do so means they risk a hefty fine and even prosecution if they have an accident."
And, the research reveals, older drivers are not alone. Across the UK as a whole, a quarter of drivers have one of these notifiable conditions, but one in 10 has failed to disclose it.
"We're urging anyone that thinks they may have a condition or a disability they need to disclose to contact the DVLA and their insurer as they risk invalidating their licence and insurance if they don't."
If you're not sure whether you have a notifiable medical condition, you can check online here.
If you do, you're best off disclosing it voluntarily, and as soon as possible, as it may mean you can start driving again sooner. There are different rules for when you can drive again depending whether if your licence was voluntarily surrendered, or if it was revoked or refused for medical reasons.
The DVLA will send you a letter when your licence is taken away or surrendered, or if your application for a driving licence is refused. This tells you how long you'll to wait before getting a new licence, and you can reapply eight weeks in advance.
You'll need to complete a D1 application form and the form for your medical condition; you might also need to send evidence of your fitness to drive.
Motorists over 65 with notifiable medical conditions
Physical disability 11%
Heart conditions 6%
Stroke or mini stroke 3%
Diabetes controlled by insulin 2%
Visual impairment 1%
Brain conditions or severe head injuries 1%