back seat driver

So, the other day I was driving my hubby to pick up his car when we had a little altercation.  He tried to tell me what route to take and I resented his manners - His route wasn't even better than mine (seriously).  I rarely rarely drive when H is with me - and I must confess that it is very easy for me to let him drive.  I get to relax (unless we're lost and I'm on map reading/direction-asking duty) and it seems to be the only time I remember to file my nails.
But this little altercation made me think that I need to assert my rights and help H learn to be patient as a passenger.  Wait, did I say patient?  I meant QUIET.  Argh.  If I constantly told him where to turn (even when we're blocks from our house) as well as when to brake - we'd... We probably. . . it doesn't bear thinking about.  
My brilliant solution was to say that "From now on, when we take my car, I'll drive."  I have driven a few times since, although not every time, and it has already caused some conflict.

Conflict #1
We were heading to some friends' house for dinner, and I guess I said "I'll drive" in a way that H found insulting or unpleasant - plus he was practically sitting in the driver's seat already.  So, he got out, fuming - and sat in the back seat.  Yes, you heard me correctly.  Then, to show him how I was not bothered, I sang as I drove.  He had to show me that he knew why I had demanded to drive by telling me that it was because I wanted to show that I was not being controlled... No need to go into that.  I did point out, however, that no matter how upset I might have been at any point in any one of our numerous car trips, I had never sat in the back because of it. Always nice to have one irrefutable fact in one's arsenal.  But, no fears, there was no heavy bombardment between back and front seats; we had a nice dinner. 

Conflict #2
We were driving somewhere with an unfamiliar route and H was driving slowly and making the man behind us impatient.  That driver was a jerk about it, yelling at H for slowing down to look for our turn (this is on a street with a 25 mph speed limit, so it's not like we were holding up highway traffic).  Anyway, H got upset and then didn't turn when he should have (on purpose?  to bother the guy?).  H was kind of arguing back with the guy with hand symbols... It was nothing rude, but it bothered me that he couldn't ignore this person and that he let it affect him and his driving.  So, on the way back I did apply my rule; we were in my car, and I drove.  H was livid but I stated my case pretty clearly, and - I think he (secretly) admitted that I had a point.  Before we got home (5 minute drive) we had already forgiven and forgotten.

Sigh...

P.S.  I admit that, in general, H is a better driver. But, I think that the rule shall still be imposed about 50% of the time.

P.P.S.  Amazing Almost Invisible woman can predict the future... We will use H's car more often for family errands.