After the 50" Bridge, the road becomes a narrow two-track with some sections of single track only passable on foot or dirt bike (yes, I include Mt bikes). Occasionally, 4x4s or SxS attempt it, but this usually ends with equipment at the bottom of a slide (see pics)
pot holes - gets better after first 300 metres
1st kilometer of this road is definitely not "impassable", I used to connect to Chilliwack Lake Road coming from "Little Tamahi 1000"