text: According to MoDOT on EB 64 there's 16'2" of clearance under McKnight, but the sign does indeed say 15'9" so I've marked the way at a 15'9" as that's the legal restriction.
  
  Also marked WB under McCutcheon at 15'9" as well.
  
  EB under McCutcheon has no restriction so left it unrestricted, WB under McKnight has no restriction either but there's no way to get to it without passing under the height restricted McCutcheon bridge.