My husband has always been an excellent driver. He was diagnosed with Alzheimer's but is in denial - says it is just an age related problem and there is no reason he can no longer drive. I and my children are in a constant state of worry about this.
How is his driving? Is the car scratched up? Any accidents? Does he get lost and wander? Getting the keys away from elders is difficult. You can search this site for very good articles,info, and discussions on this topic. I'll be facing this with my dad very soon.
Don't forget, when we take away something from a person [such as driving] we need to replace it with something else to help them feel the still have their freedom. New forms of transportation will be needed.
Here are some good articles from Aging Care. https://www.agingcare.com/Driving-Travel