Since 1999, the entire Kentucky portion is a four-lane divided highway; in some of the larger cities, there are additional traffic lanes present in both directions. In northeastern Kentucky, from the I-64 junction north into Ohio, some sections are four-lanes undivided, with a double yellow line instead of a median. These are the oldest four-lane sections of US 23 in Kentucky which were upgraded in 1950s and 1960s before divided highways became the design standard. They can be found on US 23 in the cities of Catlettsburg, Ashland, and Russell.