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 600 to 699 that do not have portions within the State Primary and State Secondary systems.
Kentucky Route 702 (KY 702) is a 2.855-mile-long (4.595 km) supplemental state highway in southwestern Elliott County that runs from a point along Neal Howard Creek Road southwest of Little Sandy to Kentucky Route 7 at Little Sandy.
Kentucky Route 714 is a 8.733-mile-long (14.054 km) rural secondary highway in southeastern Shelby County. The highway begins at a four-legged intersection in the village of Southville. KY 44 heads south along Mount Eden Road and west along Southville Pike, KY 53 heads north along Mount Eden Road, and KY 714 heads east along Hempridge Road. KY 714 meets the eastern end of KY 2866 (Woodlawn Road) and curves north to Hemp Ridge, where the route crosses a tributary of Guist Creek and an R.J. Corman Railroad Group line. The highway crosses over I-64 with no access and meets the eastern end of KY 1790 (Hooper Station Road) near Hooper before reaching its northern terminus at US 60 (Frankfort Road) south of Guist Creek Lake and west of Clay Village.
Kentucky Route 718 is a 10.813-mile-long (17.402 km) rural secondary state highway in eastern Knox County that runs from Kentucky Route 223 and Walker Road at Dewitt to Paint Gap Branch Road and Pigeon Fork Road northeast of Erose via Walker and Erose.
Kentucky Route 730 is an 11.784-mile-long (18.965 km) rural secondary highway in eastern Lyon County. The highway begins at KY 903 north of Lamasco. KY 730 heads northwest and crosses Sand Hollow Creek and the Eddy Creek arm of Lake Barkley. The highway meets the eastern end of KY 818 before crossing Glass Creek at its junction with KY 293 at Saratoga. KY 730 runs concurrently with KY 293 west to the latter route's terminus at KY 93. Along the way, the routes have two junctions with KY 818 and a diamond interchange with I-24. At the KY 93–KY 293 junction, KY 730 also meets the eastern end of KY 1055. KY 730 heads north along KY 93 and splits west at the south city limit of Eddyville. The highway meets the western end of KY 1055 shortly before the highway reaches Lake Barkley, where the highway turns onto Water Street, which passes between the lake and the Kentucky State Penitentiary, to its terminus at a dead end.
Kentucky Route 740 is a 13.807-mile-long (22.220 km) rural secondary highway in northeastern Barren County. The highway begins at US 68 and KY 80, which run concurrently on Edmonton Road, just east of the city of Glasgow. KY 740 heads northeast along Coral Hill Road, which crosses Beaver Creek and meets the western end of KY 2131 (French Mill Road) at Coral Hill. The highway parallels and crosses Duff Branch and intersects KY 70 (Hiseville Main Street) in Hiseville. KY 740 continues northeast along Hiseville–Park Road, which crosses Blue Spring Creek and intersects KY 571 (Seymour–Park Road) at Park. The highway parallels the Barren–Metcalfe county line to its terminus at KY 677 at the Barren–Hart county line very close to the Barren–Metcalfe–Hart county tripoint. KY 677 heads north onto Hart County and southeast into Metcalfe County.
Kentucky Route 743 is a 12.914-mile-long (20.783 km) rural secondary highway in northeastern Warren County and southern Edmonson County. The highway begins at US 31W (Louisville Road) west of Tuckertown. KY 743 follows Boiling Springs Road, which heads northwest to its junction with KY 2630 (Fairview Boiling Springs Road) then heads north toward the Warren–Edmonson county line. The highway crosses Little Beaverdam Creek south of the county line and meets the eastern end of KY 1749 (Wingfield Church Road). KY 743 continues along Chalybeate School Road, which turns east toward Chalybeate. The highway crosses Alexander Creek, meets the northern end of KY 2326 (Otter Gap Road), and meets the southern end of KY 3611 just west of its northern intersection with KY 101 (Chalybeate Road) south of Chalybeate. KY 743 runs concurrently south with KY 101, then the former highway turns east onto New Grove Road. The highway crosses Beaverdam Creek on its way to its end at KY 422 (Pig Road) south of Pig.