My Dad was in that same situation. He and my mom had come down to watch my son play basketball at a neighboring high school.
After the game I was following him out to the freeway and watched him run a stop sign.
When I asked my mom about it she thought I was talking about the red light he turned right through without stopping. I hadn’t seen that one. She hadn’t seen the stop sign.
Right then and there we decided he couldn’t drive anymore. To convince him we had him see a doctor about his declining memory.
When the doctor recommended that he no longer drive my dad couldn’t argue it. He never drove again.
It wasn’t easy to do and it was hard on my dad.
The thought of him hurting himself or even worse somebody else was too much to overlook. It had to be done.