I have a car pool co worker that does the same thing.
My brother in law does it as well.
It is totally irresponsible.
I have given them a look, but I have not said anything.
I didn't have the guts to say anything to either of them.
They know what they are doing, they probably know that it makes everyone feel scared as well.
In my mind I think, if they crash, and I survive, I will have to sue the living hell out of them.
But, I could not tell them that. That would end the relationship.