Complex sentence: In Arkansas, of Interstate-grade US 67 runs from I-40 to US 412 in Walnut Ridge--leaving a segment of of US 67 that still needs to be upgraded to interstate standards in northeast Arkansas and southern Missouri.
Split into simpler sentences: In Arkansas, of Interstate-grade US 67 runs from I-40 to US 412 in Walnut Ridge. This leaves a segment of of new Interstate-grade highway along US 67 that still needs to be built in northeast Arkansas and southern Missouri.