We used a weird Iron frame I think it is called a grader but I'm pretty sure I've messed up the true spelling of the object. It would be dragged over the road and it would smooth out most of the pot hole but you still need to use a shovel and fill in the deep ones with gravel and some gritty sand.
Buy an old 5 tonne four post car hoist. The rails can be used as a bridge, and they are strong enough to take 8 ton. When they have hydraulic problems they are only worth scrap metal price of maybe 1 or 2 hundred dollars! I used to sell them all the time to farmers for creek crossings etc.
Go to an automotive workshop machinery place, (Some large tool shops have workshop equipment and ask them for a non working one, that is traded or ask them to ring you when they get one, or go to an automotive workshop that is getting a new one and buy the old one off the floor. You also see them advertised in trading post type mags.If you keep your eyes open you will sometimes see them laying out the back, because they could not get even $100 bucks trade in. I sold them out of my own business for some years, so they are out there.
the Length of a span is about 14-16 foot. If you weld a few together keep some of the other parts to build the support. Each span alone will carry 5 to 8 ton, but if you are going to make it long, you will need some support. The rest of the hoist can be used for this.The best steel is in the very old Ravaglioli,(Italy) Nisselco,(Japan)Bishamon or American BendPack. Any of these will exceed their listed weight capacity by several ton. All the brands listed were sold in most countries.
Yeah, you are smart. Thanks for the help. I am going to mention this to the family and see what they think about it. I almost wish I had a huge plastic cover to cover the road with and not have to worry about it. I know ya cant do that though.
Another thought. If you send me a pic of the road, I may have some other ideas. Spent a lot of time putting in roads in the bush, so have some more uncommon experience to call on and your welcome to it.