Deciding when an older adult is no longer fit to drive is a challenging issue with no clear answer. When it comes to dementia, the decision can be especially tricky. A recent study in the journal Neurology found that as many as 76 percent of people with mild dementia are still able to pass an on-road test and drive appropriately. Yet virtually all dementia sufferers will have to stop driving eventually, as the disease worsens and memory, spatial orientation, and cognitive function decrease over time. Earlier this year, the American Academy of Neurology released new guidelines to help determine when people with Alzheimer’s disease or other forms of dementia should stop driving.

Caregivers are frequently the first line of defense when it comes to reporting unsafe driving in a person with dementia, and doctors should listen to what they have to say, according to the American Academy of Neurology’s report. “Caregivers are often proven correct when they report dangerous driving,” says Peter Rabins, M.D., M.P.H., director of the division of geriatric psychiatry at Johns Hopkins and a Health After 50 board member. “They are more likely than the patient to give a realistic assessment of the patient’s driving abilities.”

But the most reliable measure of a dementia sufferer’s driving ability is a driving test. If a doctor has doubts about a patient’s fitness to drive, he or she may refer the patient for an on-road driving test, according to Dr. Rabins. Some states actually mandate behind-the-wheel road tests by the Department of Motor Vehicles for older drivers to renew their licenses, while other states allow occupational therapists trained to assess driving ability to evaluate patients. States also differ in physician requirements for reporting a driver who is too impaired by dementia to drive.

Often, enforcing a decision that a person with dementia is unfit to drive comes down to the patient’s family or caregiver. Dementia patients may forget they were told not to drive or not agree with the assessment that they are unfit to drive. It’s a very difficult topic to approach, but beginning discussions about driving with the person early on, reducing the need to drive, and arranging alternative transportation can help make for a smoother transition to life after driving.

How can you tell if a driver with dementia may no longer have the skills needed behind the wheel? If someone shows one or more of the signs below, it’s time to have a serious conversation with the driver and his or her doctor:

• Stops in traffic for no reason or ignores traffic signs

• Fails to signal or signals inappropriately

• Drifts into other lanes of traffic or drives on the wrong side of the street

• Becomes lost on a familiar route

• Parks inappropriately

• Has difficulty seeing pedestrians or other vehicles

• Has difficulty making turns or changing lanes

• Gets drowsy or falls asleep while driving

• Lacks good judgment

• Has minor accidents or near misses