In one of the forums I visit there is a post from a gentelman who made his own homemade ramps for his RV.
He basically used my pattern Save I am not sure if he use 1x tread width or 2x (I used 2x) he used a whole lot more slabs though. His is designed for "Top of ramp" parking only I would make one change to his design.
I would put a "Stop" at the end so you do not drive off, this could be nothing more than 2x tread width mounted vertical extending about 3-4 inches above the top slab. (in fact that is exactly what I'd use)
I rather like mine.
14" would be about 19 slabs of 1x or 9 2x with a 1x base.