U.S. Route 13 (US 13) runs along the Atlantic coastline for over , passing through five states. Along its route, it possessed numerous special routes, which are all loops off the mainline US 13. At present, there are at least 15 special routes in existence: two in North Carolina, five in Virginia, two in Maryland, four in Delaware, and two in Pennsylvania. 13 others have existed in the past but have been deleted.

North Carolina

Bethel business loop

U.S. Highway 13 Business (US 13 Bus.) is a business route of US 13, passing through Bethel in the state of North Carolina. It is entirely overlapped with North Carolina Highway 11 Bus. (NC 11 Bus.). The route branches from US 13 just south of the town and follows South Main Street through the town, intersecting US 64 Alternate (US 64 Alt.) within. It rejoins US 13 just south of its interchange with US 64.

Major intersections

Windsor alternate route

U.S. Highway 13A (US 13A) was an alternate route of US 13 serving Windsor, North Carolina. Established by 1957 when mainline US 13 was bypassed west of Windsor, the alternate route followed the original alignment through downtown Windsor. In 1960, it was redesignated as a business route.

Windsor business loop

U.S. Highway 13 Business (US 13 Bus.) is a business route of US 13 serving Windsor, North Carolina. It begins by following US 17 off the concurrency with US 13 south of the town but leaves US 17 at the very next intersection, following South Granville Street. It then turns onto West Granville Street, where it follows NC 308, and then north on North King Street, leaving behind NC 308. US 13 Bus. continues north along King Street until it rejoins US 13 north of the town.

Major intersections

Virginia

Suffolk business loop

U.S. Route 13 Business (US 13 Bus.) is a business route of US 13 serving the city of Suffolk in the state of Virginia. It consists of the original routing of the highway before mainline US 13 was rerouted onto a freeway bypass to the west and north of the city. It begins near Suffolk Executive Airport, where US 13 leaves the roadway at a trumpet interchange, traveling west, while US 13 Bus. continues north on Carolina Road concurrent with State Route 32 (SR 32). As it travels deeper into the city, it intersects Washington Street, which carries SR 337, and becomes concurrent with SR 10. The three routes follow Main Street north until it meets US 58 Bus. and US 460 Bus. Here, US 13 Bus. joins the two business routes and heads east on Constance Road. The name changes to Portsmouth Boulevard and US 13 Bus./US 58 Bus./US 460 Bus. cross SR 337. The three-route overlap of business routes rejoin their mainline route, US 13/US 58/US 460, at a directional interchange (with no access to the southbound/westbound carriageway from the northbound business route) and resumes toward Norfolk.

Major intersections

Norfolk spur route

Cheriton business loop

U.S. Route 13 Business (US 13 Bus.) is a business route of US 13 serving Cheriton in the state of Virginia. The route begins at an intersection with mainline US 13 and SR 184, where SR 184 goes westward and US 13 Bus. leaves to the east of US 13. The route follows Bayside Road for its entire length, providing access to Oyster via Sunnyside Road.

Major intersections

Cheriton bypass route

Eastville business loop

U.S. Route 13 Business (US 13 Bus.) is a business route of US 13 serving Eastville in the state of Virginia. It is a two-lane road which follows Courthouse Road for its entire length. It begins in Stumptown, where it leaves US 13 at an intersection to the west, passes through Eastville, and recombines with US 13 north of town in Kendall Grove. The route provides access to Old Town Neck Drive, which leads to the Chesapeake Bay.

Major intersections

Eastville bypass route

Exmore business loop

U.S. Route 13 Business (US 13 Bus.) is a business route of US 13 serving Exmore in the state of Virginia. It begins with an intersection south of town with US 13, parallel to a railroad alignment, and carries Exmore's Main Street. In town, it intersects SR 183 before leaving Main Street for Lincoln Avenue; Main Street continues as SR 178. Lincoln Avenue sends US 13 Bus. back to its parent just south of the Accomack County line.

Major intersections

Exmore bypass route

Onley–Accomac business loop

U.S. Route 13 Business (US 13 Bus.) is a business route of US 13 serving Onley, Tasley, and Accomac in the state of Virginia, weaving across the parent US 13 several times. It begins in Onley in the south with an intersection with US 13, leaving the mainline route to the east and following Coastal Avenue. It closely parallels a railroad alignment as both of them pass under the mainline US 13 with no interchange, now following the route to its west. SR 650 intersects that route just before it curves to the northeast, meeting SR 316 (Greenbush Avenue) and SR 126 (Fairgrounds Road) at a roundabout. US 13 Business heads east here and takes on the name Tasley Road as it passes through Tasley. Tasley Road carries US 13 Bus. back toward its parent, intersecting it and continuing across as it enters Accomac on Front Street. Front Street eventually expands into a four-lane boulevard just before it rejoins mainline US 13, the southbound lanes intersecting with the north bound merging into it as a ramp.

Major intersections

Tasley bypass route

Accomac bypass route

Maryland

Pocomoke City business loop

U.S. Route 13 Business (US 13 Bus.) is a business route of US 13 that passes through Pocomoke City in Worcester and Somerset counties in Maryland.

The route begins south of Pocomoke City; US 13's four-lane divided mainline curves away to the right around the town, while US 13 Bus. continues straight ahead as a two-lane town street.

After intersecting Maryland Route 366 (MD 366), the route connects with the original southern terminus of US 113, the latter having been rolled back to terminate at mainline US 13. For a time, the marooned segment was part of MD 250 but is now designated MD 250A. Continuing north, the route heads toward the city waterfront and business district, passing through a pair of intersections with traffic lights permanently set to "flash" mode due to lack of traffic.

The route soon reaches the Pocomoke River, crossing it on a drawbridge that was first constructed in the 1920s, reconstructed in the 1990s, and continues in active service today. After crossing the river, the route heads out of town into rural surroundings before terminating on US 13 at the southern terminus of MD 364.

The route was originally created as a segment of MD 675 by 1975, when the four-lane divided Ocean Highway opened around the eastern and northern edges of the town for US 13, allowing through traffic to avoid congested inner-city streets. The road was eventually designated US 13 Bus.

Major intersections

Salisbury business loop

U.S. Route 13 Business (US 13 Bus.) is a business route of US 13 in the state of Maryland. The highway runs between US 13 south of Fruitland and US 13 and US 50 on the north side of Salisbury. US 13 Bus. is a four-lane highway with divided and undivided sections that provides access to downtown Salisbury, where the highway intersects US 50 Bus., Salisbury University, and Fruitland, where the highway meets MD 513. US 13 Bus. was constructed as a new alignment of US 13 in several steps in the 1930s and early 1940s. The section of the highway through Salisbury was originally constructed with four lanes, while the portion of the highway through Fruitland and at the northern end was expanded to a divided highway in the first half of the 1950s. US 13 Bus. was designated when US 13 was moved to the Salisbury Bypass upon its completion in 1982.

Maryland-Delaware

Delmar alternate route

U.S. Route 13 Alternate (US 13 Alt.) was a alternate route extending from US 13 in Delmar, Maryland, to Hearne's Mill near Seaford, Delaware. US 13 Alt. began at US 13 south of Delmar in Wicomico County, Maryland, heading northwest into the town on two-lane undivided Bi State Boulevard. The road turned north and came to an intersection with MD 455, at which point it crossed the state line and entered Delmar in Sussex County, Delaware. The route continued north before it left Delmar and headed through rural areas, with a Pennsylvania Railroad line a short distance to the west and US 13 to the east. Farther north, US 13 Alt. entered Laurel, where it became Central Avenue. In Laurel, the route intersected DE 24 and crossed Broad Creek on a drawbridge. The road curved to the northwest and left the town and continued through rural land along Seaford Road, with the railroad tracks to the west and US 13 to the east. The route entered the town of Blades, where it headed north on and reached a junction with DE 20 at High Street. At this point, DE 20 turned north for a concurrency with US 13 Alt., and the two routes continued north, crossing the Nanticoke River on a drawbridge. Here, the road entered the city of Seaford and became Front Street, running north. On the northern edge of Seaford, DE 20 split from US 13 Alt. by turning west onto Stein Highway. From this point, US 13 Alt. left Seaford and became Bridgeville Highway, heading northeast through rural areas to its northern terminus at an intersection with US 13 at Hearne's Mill.

US 13 Alt. was designated in 1954 following the completion of a new divided highway alignment of US 13 between south of Delmar, Maryland, and north of Seaford, Delaware. The route was decommissioned in 1957. By 1983, the portion of the former route in Maryland was designated as a section of MD 675. The former route in Delaware is state-maintained and is designated as Road 13. Despite the fact that the road has been decommissioned, locals in Wicomico and Sussex counties still refer to the route as "Alternate 13" or "U.S. Route 13A".

Major intersections

Delaware

Bridgeville business loop

U.S. Route 13 Business (US 13 Bus.) is a business route of US 13 that passes through the town of Bridgeville in Sussex County, Delaware. The business route begins at an intersection with US 13 and DE 404 south of Bridgeville, where it heads west concurrent with DE 404 Bus. as four-lane divided South Main Street. The road immediately curves to the north as it passes to the west of businesses, narrowing into a two-lane undivided road. The route heads north-northwest through farmland before heading into Bridgeville, where it passes homes. In the center of town, DE 404 Bus. splits from US 13 Bus. by heading to the west. US 13 Bus. becomes North Main Street and curves to the north-northeast, leaving Bridgeville and heading through farmland with some development. The business route has a junction with Redden Road before it reaches its northern terminus at an intersection with US 13/DE 404 only accessible to and from the southbound lanes of US 13. US 13 Bus. has an annual average daily traffic count ranging from a high of 6,171 vehicles at the north end of the DE 404 Bus. concurrency to a low of 3,429 vehicles at the northern border of Bridgeville.