I built a loading ramp for my wagon and SUV. It's made from two 6-ft long 1x10's. I designed it to work with both Silent Partner Edges and Lobster Elites. Cost me about $25 in materials. Edges were rounded off with an orbital sander to make it easy to grab and throw in the vehicles. Used a rub-on polyurethane to keep the wood from drying out. Stapled on some carpet where it touches the car and pavement.
You could also use a folding dog ramp, but the models with wider planks cost ~$100.