Complex sentence: About north of Marcellus, Route 174 crosses Nine Mile Creek; the bridge itself is designated as NY 174X, which is an internal designation used by NYSDOT and not signed as such.
Split into simpler sentences: About north of Marcellus, Route 174 crosses Nine Mile Creek, and the bridge itself is designated as NY 174X. This is an internal designation used by NYSDOT and is not signed as such.