Input (grade 13): While not part of the system's early plans, the turnpike was eventually incorporated into the Interstate system in late 1956, and is designated today as four different Interstate Highway routes: I-35, I-335, I-470, and I-70.
Output (grade 6): However, it became part of the system in 1956. Parts of the turnpike also are parts of four Interstate Highways: I-35, I-335, I-470, and I-70.