Kentucky supplemental roads and rural secondary highways are the lesser two of the four functional classes of highways constructed and maintained by the Kentucky Transportation Cabinet, the state-level agency that constructs and maintains highways in Kentucky. The agency splits its inventory of state highway mileage into four categories: The State Primary System includes Interstate Highways, Parkways, and other long-distance highways of statewide importance that connect the state's major cities, including much of the courses of Kentucky's U.S. Highways. The State Secondary System includes highways of regional importance that connect the state's smaller urban centers, including those county seats not served by the state primary system. The Rural Secondary System includes highways of local importance, such as farm-to-market roads and urban collectors. Supplemental Roads are the set of highways not in the first three systems, including frontage roads, bypassed portions of other state highways, and rural roads that only serve their immediate area.
The same-numbered highway can comprise sections of road under different categories. This list contains descriptions of Supplemental Roads and highways in the Rural Secondary System numbered 500 to 599 that do not have portions within the State Primary and State Secondary systems.
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Kentucky Route 500
Kentucky Route 500 is a rural secondary highway in western Daviess County. The highway begins at KY 56 at St. Joseph. KY 500 heads north toward Curdsville, meeting the west end of KY 456 south of the village. The highway enters the village along Main Street then passes through three right-angle turns before reaching a dead end at the confluence of Panther Creek with the Green River.
Kentucky Route 501
Kentucky Route 501 (KY 501) is a state highway that runs from Kentucky Route 910 at Phil to U.S. Route 27 northeast of Kings Mountain via Kings Mountain.
Major intersections
Kentucky Route 502
Kentucky Route 502 (KY 502) is a state highway in Hopkins County that runs from Kentucky Route 109 and Bone Road at Rabbit Ridge to Old Morganfield Road and Balls Hill Road north of Nebo via Nebo.
Major intersections
Kentucky Route 503
Kentucky Route 503 (KY 503) is a state highway that runs from Kentucky Route 5 north of Princess to Kentucky Route 3105 and Industrial Road in Wurtland via Naples and Danleyton.
Major intersections
Kentucky Route 504
Kentucky Route 504 (KY 504) is a state highway that runs from Kentucky Route 32 just east of Elliottville to Kentucky Route 7 at Green via Ault and Gimlet.
Major intersections
Kentucky Route 505
Kentucky Route 505 (KY 505) is a rural secondary highway in eastern Ohio County. The highway extends from US 231 southeast of Cromwell north to KY 878 at Olaton via Oak Grove, Select, Baizetown, and Windy Hill. KY 505 begins at US 231 () southeast of Cromwell. The highway heads northeast, bridges the West Prong of Indian Camp Creek, and crosses over the William H. Natcher Parkway. The highway gradually curves east as it crosses three branches of Indian Camp Creek and passes through Oak Grove and Select. At Baizetown, KY 505 meets the northern end of KY 1118 and turns north. The highway crosses the Western Kentucky Parkway on its way to Windy Hill, where the route meets the western end of KY 2713. KY 505 crosses over the Paducah and Louisville Railway shortly before its junction with US 62 east of Rosine. The two highway run concurrently east until KY 505 splits north near Horse Branch. KY 505 continues along Dan Road, which crosses Muddy Creek and a branch of Caney Creek before reaching its northern terminus at KY 878 at Olaton.
Major intersections
Kentucky Route 506
Kentucky Route 506 (KY 506) is a state highway that runs from Kentucky Route 902 northeast of Enon to U.S. Route 60, Kentucky Route 91, and West Depot Street in downtown Marion via Piney Fork.
Major intersections
Kentucky Route 507
Kentucky Route 507 (KY 507) is a rural secondary highway in eastern Christian County and northern Todd County. The highway extends from KY 107 in Hopkinsville east to KY 106 and KY 178 at Claymour via Allegre. KY 507 begins at a three-way intersection with KY 107 in the city of Hopkinsville. KY 107 heads west along East Seventh Street and northeast along Greenville Road, and KY 507 heads east along East Seventh Street. Further east, KY 507 splits northeast along Butler Road while KY 1979 continues along East Seventh Street to US 68 and KY 80. KY 507 heads northeast and meets the western end of KY 508, which continues on Butler Road while KY 507 continues on Pilot Rock Road. The route twice crosses Lower Branch of the North Fork of the Little River on its way to Pleasant Hill.
KY 507 crosses the South Fork of the Little River before crossing the Christian–Todd county line. The highway continues east and meets the eastern end of KY 189 (Moss Road) just west of the route's bridge across Buck Fork Creek. KY 507 crosses the Shelton Branch of the Pond River just west of Allegre, where the route intersects KY 171 (Allegre Road). The highway continues along Highland Lick Road, which crosses the Pond River and intersects KY 181 (Greenville Road) south of Cedar Grove. KY 507 continues southeast to Claymour, the site of the route's terminus at a four-way intersection with KY 106 (Sharon Grove Road) and KY 178, which takes over the course of Highland Lick Road.
Major intersections
Kentucky Route 508
Kentucky Route 508 (KY 508) is a rural secondary highway in eastern Christian County and western Todd County. The highway begins at KY 507 east of Hopkinsville. KY 507 heads west along Butler Road and northeast along Pilot Rock Road; KY 508 heads southeast along Butler Road, which veers east at its junction with KY 1716 (Overby Lane). The highway crosses the South Fork of the Little River just west of its junction with KY 1843 (Vaughns Grove Fairview Road). KY 508 passes through Honey Grove before crossing the Christian–Todd county line. The highway follows Butler Road through Britmart to Tabernacle. From there, KY 508 follows Liberty–Britmart Road to its east end at Liberty.
Major intersections
Kentucky Route 509
Kentucky Route 509 (KY 509) is a rural secondary highway in northwestern Nelson County. The highway begins at KY 245 (New Shepherdsville Road) south of Samuels. KY 509 heads north along Samuels Loop to Samuels, where the route meets the eastern end of KY 3207, also part of Samuels Loop, and has a grade crossing of an R.J. Corman Railroad Group rail line where it turns east onto Samuels Road. KY 509 heads northeast along Samuels Creek to its mouth at Froman Creek and crosses the latter creek, where the route continues east to Coxs Creek. There, the highway meets the southern end of KY 2739 (Lenore Road) and intersects US 31E and US 150 (Louisville Road). KY 509 continues east as Fairfield Road, which crosses Cox Creek and reaches its eastern terminus at KY 48 (Highgrove Road) west of the city of Fairfield.
Major intersections
Kentucky Route 510
Kentucky Route 510 (KY 510) is a state highway that runs from Kentucky Route 221 at Pine Mountain to Kentucky Route 463 north of Gordon via Gilley.
Major intersections
Kentucky Route 511
Kentucky Route 511 (KY 511) is a state highway that runs from U.S. Route 25W east of Youngs Creek to Kentucky Route 26 and Youngs Lane at Rockholds via Walden.
Major intersections
Kentucky Route 512
Kentucky Route 512 (KY 512) is a state highway that runs from Kentucky Route 395 at Birdie to U.S. Route 127 east of Alton via Alton Station and Alton.
Major intersections
Kentucky Route 513
Kentucky Route 513 (KY 513) is a state highway that runs from U.S. Route 62 at Fox Creek to Harry Wise Road and Gilberts Creek Road east of McBrayer via McBrayer.
Major intersections
Kentucky Route 514
Kentucky Route 514 (KY 514) is a state highway in Caldwell County that runs from Ferguson Road at the Caldwell-Lyon County line west of Hopson to Kentucky Routes 126 and 128 northwest of Cobb via Hopson.
Major intersections
Kentucky Route 515
Kentucky Route 515 (KY 515) is a state highway in Caldwell County that runs from Kentucky Route 903 to Kentucky Route 139 south-southeast of Princeton.
Kentucky Route 516
Kentucky Route 516 (KY 516) is a state highway in Bell County.
Kentucky Route 517
Kentucky Route 517 (KY 517) is a state highway in Allen County that runs from Kentucky Route 252 to Bailey Point Road and Hix Road northeast of Cedar Springs along the shore of Barren River Lake.
History KY 517 was formed after 1958.
The original KY 517 ran from US 231 southeast of Greenwood south to KY 240; this became part of KY 622 when it was extended north.
Kentucky Route 518
Kentucky Route 518 (KY 518) was a state highway in Lincoln County. It ran from KY 78 in Hustonville via Mt. Salem Road to KY 198 in Mt. Salem. The highway was decommissioned on October 22, 2001, and the road (along with intersecting KY 1562) was given to Lincoln County.
Kentucky Route 520
Kentucky Route 520 (KY 520) is a state highway in Henderson County that runs from Kentucky Route 136 southeast of Anthoston to Kentucky Route 416 and Upper Delaware Road at Coraville.
History KY 520 was formed by 1958.
The original KY 520 ran from KY 65 (now KY 259) in Westview east to Mook; this became part of KY 690 in 1954-1957 when it was extended southwest.
Kentucky Route 521
Kentucky Route 521 (KY 521) is a state highway in Laurel County that runs from Kentucky Route 1189 southwest of Lesbas to Kentucky Route 80 southwest of Brock.
Major intersections
Kentucky Route 522
Kentucky Route 522 (KY 522) is a state highway in Harlan County that runs from U.S. Route 119 and Ross Drive in Rosspoint to Kentucky Route 160 at Sand Hill via Rosspoint, Rhea, Dillon, Laden, Nolansburg, Totz, Dione, Hiram, and Chad. It is the original alignment of US 119.
History KY 522 was formed when US 119 was rerouted in 1973–1977.
The original KY 522 ran from Kuttawa to US 68 in Twin Lakes; this was cancelled when most of this route was inundated by the creation of Lake Barkley in 1964; surviving parts are now First Street, Kuttawa Lane, Brandon Chapel Road, and Big Bear Highway.
Major intersections
Kentucky Route 523
Kentucky Route 523 (KY 523) is a state highway in Nelson County that runs from Kentucky Route 245 and Marr Lane southeast of Deatsville and going through Deatsville and Lenore. KY 523 was extended on its eastern end upon the completion of a realigned section of Louisville Road (US 31E / US 150). KY 523 now follows the former alignment of Louisville Road from its former terminus 2 miles south of High Grove northward for approximately 4½ miles to the new Louisville Road. That is south of the Salt River bridge at the border between Spencer County and Bullitt County. The new section also includes a 1½ mile concurrency with Kentucky Route 48, which was also slightly extended to meet up the newer incarnation of US 31E / US 150
Kentucky Route 524
Kentucky Route 524 (KY 524) is a state highway in Oldham County that runs from and to U.S. Route 42 via Westport.
Major intersections
Kentucky Route 525
Kentucky Route 525 (KY 525) is a state highway in Trigg County that runs from Kentucky Route 164 west of Roaring Spring to Kentucky Route 139 south of Cadiz.
Major intersections
Kentucky Route 529
Kentucky Route 529 (KY 529) is a state highway in Washington County that runs from Valley Hill Road and Croakes Station Road at Booker to Kentucky Route 55 west of Mooresville.
Kentucky Route 530
Kentucky Route 530 (KY 530) is a state highway in Adair County that runs from Kentucky Route 55 and Keltner Road to Kentucky Route 2971 north of Columbia.
Kentucky Route 531
Kentucky Route 531 (KY 531) is a state highway in Adair County that runs from Kentucky Route 80 east of Ozark to Kentucky Route 206 at Christine via Craycraft.
Major intersections
Kentucky Route 532