If you have a small SUV, you can try using a household object as a step instead of buying a ramp. A friend uses a milk crate. My dog with HD uses an extra-large plastic kitty-litter pan bought just for this purpose, turned upside down:
The plastic litter pan stays behind my driver's seat to pull out for him. It's lightweight, doesn't take much space and is easy -- the ramps and dog-steps are much heavier.