The section of DE 15 between DE 14 and US 13 serves as part of a secondary hurricane evacuation route from coastal areas in southern Delaware. The portion of the route along the DE 6 concurrency west of Clayton and between Alley Mill Road and Caldwell Corner Road in southwestern New Castle County is part of the Harriet Tubman Underground Railroad Byway, a Delaware Byway. DE 15 has an annual average daily traffic count ranging from a high of 30,257 vehicles at the Walker Road intersection in Dover to a low of 806 vehicles at the Caldwell Corner Road intersection south of Middletown. The portions of DE 15 concurrent with US  13, between DE 8 and Scarborough Road, and along the DE 299 concurrency are part of the National Highway System.