How thick should the gravel be on a reconstructed road?
The thickness should vary depending upon the traffic (mostly due to trucks). As a starting point the South Dakota Gravel Roads: Maintenance and Design Manual has basic information about thickness design for gravel roads in Appendix A. New York State is in Climatic Zone III. The design catalog starting on page A10 is a good starting point for determining a minimum thickness. However, we do not recommend using less than 12 inches of gravel in any case. Even though the pavement structure is fine, with maintenance you will actually lose gravel and in a few years the thickness will be too thin.
You can use the same information for designing the thickness of a chip sealed road, just be sure the gravel is as clean as possible (5% or less is preferred). See the Cornell Local Roads Program Tech Tips on gravel for more information on what makes a good gravel for a base or surface.