Most drives in my area are crushed limestone, which is entirely different from gravel. Gravel is round, and will roll, while crushed stone is angular. Here, limestone is crushed in a quarry, while gravel is dipped with a dragline. My inlaws thought a pea gravel parking area would be great. But, a vehicle will sink into it as it doesn't really pack...it just rolls out of the way. You can actually feel the vehicle bog down when entering it.
If this is a new road, you may want to consider a large stone for a base, then top dress with a smaller stone. If the base is solid, then you probably only need some smaller stone on top. I use fives and eights for a top dressing, but most around here use #53 stone, which contains a lot of fines to help it pack.
If you want to be fancy, #11 makes a beautiful top dressing but will tend to track....it sticks in the tread on automotive tires, and even on shoes.
