Is your travel time flexible? Doing it at night might be the easiest. I'm guessing you are travelling alone so there's no option of having one person sit in the back with baby?
Take breaks, I guess the bridge is the least flexible part cause once you're on it you just have to keep going - maybe save that part for naptime if you can? How is she in the car normally? When DD was little she would often get fussy when I was driving with her. I would often put my hand over her seat back (she was in the center rear seat) so I could touch her and let her suck on my finger (a comfort thing she had leftover from when we were finger-feeding as a tiny baby). Also have a bunch of baby-safe toys in the front seat beside you so you can periodically hand her things - my DD would toss them after a few minutes when she got impatient but it worked for a few minutes and then I'd move onto the next thing in my basket. Simple things like containers with rattling coins, non-toy things that may be new to her, anything that she won't choke on or hurt herself with of course.
Sing along with the radio, have conversations with her, that's pretty much what I did. And really do take lots of breaks to feed and change her, and generally give her a break. Good luck!