My manager calls in to the morning stand-up meeting while driving to the office.

This is dangerous, not just for him but for other drivers.

I want so badly to say something but he's my manager and I'm afraid of reprisal.

He wouldn't listen to me anyway.

Well, maybe he uses a headset. Or his car has call integration.

@PrivateGER that would make it legal, but not less dangerous. His mind is never a 100% on the road, where it should be.

Personally I find that if you care about the situation so much that you share it with us on here, he should know.

Do let him know that it’s not to bother him or anything, but it concerns you that he does this sort of thing. I think regardless of position, people should be able to listen to each other every once in a while and not take any reprisals. But just to be sure, look at your approach and what’d be nicer is if you can adapt your message in a way he’ll like/appreciate.