waverider is right...
don't try to communicate to him while he is yelling you are in a car and could make it worse.
now what i did after this and i got through this is i set boundaries, if he does this again for one week i will take my own car will not ride with him
i set a limit that i could stick to one week a day what ever so he knows you mean business. I did this if the kids were in the car and i did this when he acted up when they weren't in the car,
my husband use to road rage horrible... . I had to set boundaries, it took some time because things got worse, before better then slowly he stopped road rageing, and yelling.
I set a boundary you rage in a car at me, i won't ride with you for one week if i drive and you rage you will be asked to leave the car. I only had to do this once due to he spent all day walking and finally when he cooled down called me... to pick him up.

Things always get worse before better due to you changing things, and hopefully once he understands u mean buisness he will follow nothing changes with out change...