Almost half the elderly drivers who caused fatal traffic accidents in Japan last year were considered to have cognitive impairments such as dementia, police data showed Thursday.

Of 385 such drivers aged 75 and over, 28 were suspected of having dementia and 161 may have had reduced cognitive functions, according to the National Police Agency. They were among people who took a cognitive test required by law when they renewed their driving license.

Japan, which has seen a rise in serious traffic accidents involving elderly drivers in recent years, introduced tougher screenings in March. Authorities suspend or take away the licenses of drivers diagnosed with dementia.

The 28 drivers who showed signs of dementia were likely to have been awaiting diagnosis by doctors.

“Family members (of senior drivers) might feel when they ride in cars driven by the seniors that the risk of accidents is high,” Hachiro Okonogi, chairman of the National Public Safety Commission, told a news conference Thursday.

“It is extremely important that such family members suggest to the senior drivers that they should avoid driving.”

Noting the correlation between serious accidents and a decline in drivers’ cognitive function, the NPA has been urging elderly drivers to voluntarily give up their licenses.

The latest police data showed 194 people died in accidents caused by those thought to have been suffering from dementia or reduced cognition.

There were 418 fatal accidents last year caused by drivers aged 75 or older, including those who have not yet taken the cognitive test.

Of these accidents, 41 percent involved vehicle collisions and 19 percent were collisions between vehicles and pedestrians. Running into guardrails or falling into runnels accounted about 40 percent.

As for causes of accidents, the highest was driving errors with 31 percent, such as erroneously stepping on the accelerator or brakes.

The revised Road Traffic Act came into force in March and introduced tougher tests for drivers aged 75 years or older to detect signs of dementia.

They are required to take the cognitive test when they renew their license or if they are ticketed for certain traffic violations.

The cognitive test checks memory and judgment.

For example, those taking the test are shown an illustration and then asked a while later to recall what it looked like.

They are also asked to draw an illustration of a clock showing a specific time. The test classifies the drivers into three groups, and the ones “suspected of having dementia” are required to undergo a more detailed test by a doctor.

If doctors diagnose the drivers with dementia, they will have their licenses suspended or revoked.

As of the end of last year, there were 5.4 million drivers aged 75 or older in the nation.