My Elderly Father Refuses to Give up His Driver’s License, Even Though He Promised to do so

I’m a female part-time worker in my 40s. My husband is a professor at a university hospital and we have three children, from elementary to high school age. I’m a female part-time worker in my late 50s. I’d like some advice about my father, who is still driving in his late 80s. He’s a small-scale farmer and delivers vegetables to a local agricultural cooperatives farm stand every day. My mother died a few years ago, and he has devoted himself to farming, perhaps out of loneliness.