Nearly 700 elderly drivers in Japan have had their licences revoked, after it was found they had late-stage dementia.
Police say screenings found about 30,000 more may be suffering, and must return for more tests.
Japan has the oldest population in the world and close to 50,000 people are diagnosed with dementia yearly.
New road traffic laws require those above 75 to undergo regular cognitive function tests.
Every year, there are hundreds of severe road accidents involving people over 75. In 1993 there were 62 cases of fatal accidents caused by people over 75.
In 2016, Japan recorded a total of 459 fatal accidents, caused by elderly drivers.
Businesses are trying to incentivise elderly drivers to give up their driver's licence, by offering them a range of products and services ranging from discounted funeral services to cheap noodles.