K-4 is the longest designated state highway in Kansas, at 369.079 miles (593.975 km). It begins north of Scott City at U.S. Route 83 (US-83) and travels eastward to US-59 near Nortonville in northeast Kansas. A segment of the highway in Saline County overlaps Interstate 135 (I-135) and US-81, and a section in Topeka runs concurrent with I-70. It also intersects several other major highways, including US-283 in Ransom, US-183 in La Crosse, US-281 in Hoisington, US-77 in Herington, I-470 and US-75 in Topeka, and US-24 northeast of Topeka.