Advancing age alone is not a sign that it's time for a driver togive up the keys.

It follows that in 2015, the Centers for Disease Control logged more than 40million U.S. drivers age 65 and older. That reflected a 50%increase over the previous data pool collected in 1999 — an upwardtrend that's likely to continue as the U.S. population of adultsage 70 and older is projected to increase from 31.7 million in2015 to 53.7 million in 2030, according to the U.S. CensusBureau.

Most government agencies recognize that being able to drivesupports an older adult's ability to remain self-sufficient, whichis one reason why states have avoided putting laws on the booksthat would require individuals to age out of their driver'slicense.

Teenagers cause most U.S. crashes

Driving research does support the idea that there are very realdangers when any potentially unfit driver, regardless of age,refuses to give up the keys.

The problem facing older drivers (and their insurers) is notthat these mature adults tend to cause more motor vehicleaccidents; teenagers have the dubious honor of being theage-based group that causes the most crashes on American roads andhighways.

The danger for older adults is that when they are involved in an accident, they face amuch higher risk of being seriously injured or killed.According to the CDC: Involvement in fatal crashes, per miletraveled, begins increasing among drivers age 70‒74, and is highestamong drivers ages 85 and older.

As a risk of a deadly accident increases, so will a driver'sinsurance premiums.

6 signs it may be time to stop driving

Here are six signs that it may be time to talk with an olderdriver about giving up the keys, largely based on research compiledby the Insurance Institute for Highway Safety.

No. 6: The driver suffers from medical conditions that mayimpact his or her ability to safely navigate a vehicle.

Impairments in memory, vision, mobility and/or medicalconditions such as arthritis or diabetes can cause drivers to react more slowly or become lessattentive.

Some of the specific medical conditions associated with losingthe skills and abilities to drive safely include:

• Dementia
• Alzheimer's disease
• Vision loss
• Heart disease
• Parkinson's disease
• Arthritis
• Diabetes

The good news is that IIHS research indicates that many olderdrivers with these conditions are more likely to self-limit theirtime behind the wheel.

However, the Institute's research also found that a portion ofolder drivers never recognize the need to adjust their drivinghabits, even when they suffer from obvious cognitivedegeneration.

AAA conducted a study in which nine out of 10senior drivers said that giving up their car would make their livesmore difficult.

No. 5: The driver takes medication that may impair response andreaction time.

As we age, we are more likely to require prescriptionmedication.

But even over-the-counter medications can impair one'sability to drive safely.

AAA compiled the following medication side effects that cancause a driver to become distracted from safely operating avehicle:

• Anxiety
• Blurred Vision
• Chest Pain
• Confusion
• Dizziness
• Disorientation
• Drowsiness
• Muscle Cramps
• Nausea

No. 4: The driver suffers from recognizable cognitivedecline.

Doctors advise looking for some very obvious signs that an olderdriver is no longer fit for the road. For instance, when a driverstops at green lights, becomes confused by traffic signage orsignals, or runs a red light, it may be time to talk about givingup the keys.

Another bell-ringer: Some older drivers become confused or lost while they're behind thewheel.

No. 3: Local roads and signs need to be upgraded.

Older drivers do better when the roads in their communities are well-maintainedand the road signs feature clear, vivid lettering anddirections.

IIHS research indicates that some relatively low-costinfrastructure improvements such as adding dedicated left-turnlanes can result in a significant reduction in senior caraccidents.

No. 2: The driver's vehicle needs to be replaced.

Newer model cars include features such as sideairbags and rear-view cameras that can help keep older driverssafe.

Alternately, some older model cars may have features (such asdated seatbelts) or maintenance issues that increase an olderdriver's chance of being seriously injured in an accident.

No. 1: There's no real reason to drive.

Simply put: The longer a person drives, the more likely theyare to be involved in an accident, and to be very badly hurt oreven killed in that accident.

An older person may significantly increase their lifespan whenhe or she makes the choice to stop driving.

The choice may be easier when older adults have ready access topublic transportation or senior rideshare programs. But not allseniors, particularly those living in rural communities, have easyaccess to alternate modes of transportation.

See also:

The best cars for senior drivers in2017

10 most dangerous states for seniordrivers

20 car crash tips and things you should know afteran accident