Doyle, Inc. of Minnesota can make the process easier and cheaper. Its tractor- mounted reclaimer is similar to an agricultural harrow disc. Pulled behind a standard mower tractor, the reclaimer cuts through sod, mixes the gravel with the fines below it, and throws the gravel one to two feet toward the pavement edge to fill the void there. A roller, or grader with roller, follows behind to pack the gravel into a smooth, tight surface. You need moisture so the gravel packs properly.
Spring is another good time for shoulder improvements.
Mower tractors are available, there's moisture in the gravel, and the weeds have died off. Using the reclaimer, crews in Minnesota were able to reclaim 48 miles of shoulder a day, the amount they did in three days using previous methods. We use it just about every time we go out and maintain shoulders. There is also a similar product from a Canadian company which mounts on a motor grader ahead of the moldboard. The manufacturer recommends it for effectively working road shoulders using fewer people than conventional methods.