This thesis studied unpaved highway shoulders, and in particular shoulders of lower volume asphalt pavements being overlaid. The primary objective was to better understand how different shoulder aggregates perform on lower volume routes with asphalt surfaces and relatively narrow shoulders. A literature review and an evaluation of a full-scale test section containing five aggregate categories in nine test sections over a thirty-four-month period were the primary efforts performed to evaluate unpaved highway shoulders. The study concluded shoulder width measurements were not especially informative, and that California Bearing Ratio measurements were only modestly informative. Crushed concrete outperformed all other aggregates, though the remaining aggregate categories (gravel, limestone, steel slag, and reclaimed asphalt pavement) also had a reasonable case for being moved forward toward possible specification updates. The primary recommendation of this thesis is to use the data contained herein to further shoulder aggregate specifications for the Mississippi Department of Transportation.