Dirt and paved road curves differ significantly, and that has nothing to do with size and surface.  This has to do with how they are constructed.

    Paved roads are laid out with circle-drawing compasses.  That doesn’t mean they are circles, but it does mean that they are regular curves.  When you enter a paved curve and give the steering wheel a "set," the road more or less holds constant.  Paved curves almost always go from straight, transition to a fixed, regular curve, then straighten out again with no irregularities in between.  This makes for easier and safer driving.

    Dirt roads usually follow Mother Nature’s lay of the land.  This leads to irregular curves.  Irregular curves mean the radius varies: They may get tighter and tighter, or straighten out faster than expected.  That may be the reason we unexpectedly slide out because it ain’t exactly what our paved mindset was expectin’.