I think this illustrates why so many road associations have just gone with the simplest solution, i.e. everyone pays the same. The more you try too hard to make it fair and equitable, the more variables someone will bring up.
You could, for example, take into consideration the number of feet of road frontage each person owns, or the assessed value of their property, or how many cars they own, or how heavy each of their vehicle is, or whether they have frequent deliveries made to their house, or how many trips per week they make over the road, or whether they always drive in the same two ruts or if they are careful to move over one tire width each trip so as to keep the road evenly packed and worn. (This last sounds ludicrous, but during mud season it can make a huge difference in a person's impact on the road.)
It has often been suggested that to be fair, each person should pay based on the length of road that they use. But consider this example: To make it simple, let's suppose a road is exactly one mile long, and has ten landowners who each own property on both sides of the road for one tenth of a mile. We can then divide the cost of maintenance of each tenth of a mile of road into ten parts to be shared by the ten owners, adding up to one hundred percent of the cost of maintenance of the whole road.
The first owner will pay only for maintenance of the first tenth of a mile of road. But since that section of road is used by all ten owners, the first person will pay only one tenth of the cost of maintaining that section of road. Each of the ten owners will contribute their tenth of the shared cost of maintaining the first tenth of a mile of road, so that between the ten of them the entire cost of maintaining that section of road is covered.
The second person will pay one tenth of the cost of maintaining that first section, which is shared by everyone, and will pay one ninth of the cost of maintaining the second tenth of a mile of road which is used by him and eight other landowners. So between the nine of them, they will cover the whole cost of maintaining that tenth of the road.
The third landowner will pay one tenth of the cost of the first tenth of a mile, plus one ninth of the cost of the second tenth of a mile, plus one eighth of the cost of maintaining the third tenth of a mile of road which is used by himself and seven others.
Calculations would continue in that fashion until you come to the tenth person in. That person will pay the entire cost of maintaining the last tenth of a mile which is used only by him, plus half of the next to last tenth of a mile which is used only by him and his closest neighbor, plus one third of the next tenth, one fourth of the next tenth, one fifth of the next tenth, etc until the first tenth, of which he pays only one tenth of the cost of maintenance because that section of road is used by everyone so all ten landowners share the cost.
So the first person contributes only 1% of the association's total road maintenance budget, but if my calculations are correct, converting all those fractions to decimals and adding them up, the last person in pays over 29 times as much, or approaching 1/3 of the association's total road maintenance budget. Is that "fair and equitable?" Chances are, the people farther in are going to refuse to pay, raising costs for filing Notices of Claim and forcing others to pay more to cover the cost of maintenance.
But that formula still doesn't take into account other variables such as each person owning a different length of road frontage, which parts of the road may have culverts that need to be maintained or replaced, which parts of the road may be prone to erosion, etc. Adding such factors to the calculation in an effort to be "fair and equitable" would be a nightmare.
I think this comes into the same sort of argument as requiring people who have no school aged children to contribute their tax dollars towards the school budget. If we all pull together for the good of the community as a whole, the burden on each of us should not be too great for any one person to bear. (If it is a hardship on someone, others should pitch in a bit extra for the sake of their neighbor.) The cost of annual road association dues may not be much more than the cost of hiring someone to plow your own driveway in the winter, yet what you get for your dollar is year-round maintenance for you AND your neighbors.
One other consideration is that in many subdivisions, each person's deed grants them a right of ingress and egress over the private road TO AND FROM the public road system. That implies that they are not allowed to use more of the road beyond their property. In my opinion, "fair and equitable" should require that each person be allowed to use the entire road or system of roads which their dues help to maintain, and to share that privilege - respectfully - with other association members who wish to do the same. They may only use it to walk their dog or to get some exercise and fresh air, but that is nevertheless a benefit, and at least a token of appreciation for contributing to the entire cost of maintaining the road.
As I said at the outset, many road associations have found that the simplest formula is best. Think of your neighbor, stop complaining, and share the burden for the good of all.