Kansas Turnpike - Design

Design

Because the Kansas Turnpike was built before the Interstate Highway System, it is not engineered to current Interstate Highway standards. Notably, the turnpike was built without a 36-foot (11 m) median. When it opened, the central reservation was a 20-foot (6.1 m) depressed median. Starting in 1985, Jersey barriers were installed along its entire length. This is similar to what the Pennsylvania Turnpike did in the 1970s, as that highway has an even narrower median. In both cases, as with all other toll roads that predated the Interstate Highway System, the highway is grandfathered from Interstate standards.

Kansas Turnpike mileposts are continuous along the entire length of the turnpike. Mile markers begin at the point where I-35 enters Kansas at the southern border. These numbers are continued along the other three interstates that make up the turnpike, rather than numbering each interstate individually, leading to discontinuous numbering on I-70—the exit numbers east of Topeka are much lower than those west of the city.

The majority of the Kansas Turnpike, from the Oklahoma state line to Topeka, was constructed with 4-inch (100 mm) asphalt. The 55 miles (89 km) from Topeka to Kansas City was built with Portland cement concrete. Curves along the turnpike are limited to 3° and grades limited to 3%. Early reports said that curves were designed to accommodate speeds of 70 to 75 mph (121 km/h). When built, the turnpike was designed to allow 18,000-pound (8,165 kg) axle loads. Minimum sight distances were kept at 725 feet (221 m).