As he is really getting on my nerves. Every time I drive, he is constantly talking to me like a driving instructor - telling me to brake all the time, telling me to stop at a zebra crossing when there's no one there, telling me to 'watch my speed' when I never speed! He has been driving half the time I have, and I have several years of NCD, never had anything so much as a car park scrape.
If a car 5 cars in front of us brakes, he's going in a loud and urgent voice 'brake brake brake!', or at roundabouts he's telling me to 'get in lane' - I manage perfectly well when he's not in the car with me, I don't need him in my ear all the time! He does things like reminds me there's traffic lights 5 miles away 
When I'm parking up, he's sighing and telling me to 'watch it' and 'straighten up now' and 'watch that car there!'
Yesterday I lost my rag with him and told him to stop it, as I don't act like that when I'm in the car with him, and it's very off putting. I told him if he carries on he's not coming in the car with me anymore.
Out of the corner of my eye for the rest of the journey, I could see him grimacing every 30 seconds. I am a perfectly safe driver, I brake in more than enough time, I always leave a safe gap. I've noticed him being the same in the car with his parents, but obviously they tell him to shut up.
today ive had enough and told him he can do all the driving all day.