Interstate 95 is a very short and poorly detailed highway (thanks to the developers) where one takes you south to Coconut Grove, and one takes you west (Atari, you should've never let people with poor I.Q's help with the development of this game, because 95 is an ODD number, and odd numbers go North and South, not South and "West"). I'm just gonna put the shield because there is no image of the highway in-game that I could find.
So pretty much it starts off as a two lane highway and later turns into a 6 lane then back to 4 lanes when you take I-95 south. If you take I-95 "west" it will only be 4 lanes all the way to the end. I'm pretty sure it is much more than 6 or 4 lanes irl.