Bingley does this too. Interestingly, he settles completely if we are travelling at speed (on a motor way or something) but really starts to make himself heard if we are driving slowly. I often wonder if he equates going slower to 'oh gee i'm about to get out for a walk!!', who knows.
He has a chew in the car but rarely does anything with it TBH. Ignoring him completely is the only thing that does any good!