ISTR this had a topic in the past, though I won't attempt to look one up ATM. I do remember examining this endpoint, throwing up my hands, and going no-build.
Re-examining the sources:
TDR & shapefiles show Main St.
Tour Book lists Inner Loop.
Of these 2 options, the no-build option (UniSt, formerly the Inner Loop) is closer to where signage disappears.