I think that is where they sprayed oil then put gravel over it, in which the gravel hardens in the oil base. Better than loose gravel but not as good as a regular surface.
This was a very common practice on subdivision streets and other paved roads with low traffic volumes in my home county - Montgomery County, Maryland.
In Montgomery County, it worked like this - first, a water tank truck would come through and "wash" the pavement to be treated. After the pavement dried (such operations were never done on rainy or cold days), an oil tank truck would put down a layer of hot oil (not quite as sticky as tar). Right after the oil truck, a chip spreader would come along and put down a generous layer of pretty finely-milled rock chips. After that, a pavement roller to get the chips to adhere (somewhat) to the oil.
For several weeks after this treatment, the paved roads would have the "look and feel" of unpaved gravel roads, but eventually the chips would adhere, and some would get washed away in the rain. After about a month, the oil truck would return and put down another layer over top of the chips to seal them in.
I do not think the county does this any longer, because people complained that the loose chips damaged their cars. The chips only did damage to cars that were going well over the 25 MPH speed limit.