Soldato
The FitBit will add a few steps while driving but not many. My normal drive to work is about 40 minutes along the back roads which are quite uneven in places and it adds less than 50 steps. 50 steps extra over 16,000 is so little as to make no difference.
Must depend on the model, I catch the bus to work and have been in the minibus at work (I work at a school) and my Zip has never recorded extra steps for those.