The former State Road 431, now simply Keystone Avenue, remains a busy route connecting U.S. Route 31 with Interstate 465 at Exit 33. It passes through the Indianapolis suburb of Carmel, allowing traffic on U.S. 31 north of Carmel a shorter route to I-465 and the east side of Indianapolis. Until the 1990s, the State Road 431 designation extended south of I-465 to 86th Street. Prior to that, it also continued south along N. Keystone Avenue to S.R.