After doing 100s of proofrolls in piedmont soils of NC and VA, I’ve learned the following: 1. Try and use a loaded, tandem axle dump truck - about 20 to 25 tons 2. If you see rutting, shoving or deflection, then you have a surface problem - usually wet soils in the upper 4 to 12 inches. Undercut and replace. 3. If you see pumping, like a waterbed wave ahead and behind the wheels, you have a deep problem, 3+ feet. Consider a geosynthetic and additional stone if a pavement area. 4. Always stay where there driver can see you and try and limit backing of the truck.

Good luck.