It appears that US 310 is signed north of I-90 up to former US 10.
This assembly at I-90 and
this one on BL 90 show US 310 continuing up to BL 90.
These signs probably aren't erroneous (outside of the one directing 310 traffic onto 90), as the MDT logs still have US 310 ending at US 10.
It should be noted that the MDT log has US 310 following 90 BL east to the end, MDT GIS has no mention of 310 north of the southern 212 junction, and the AASHTO log has not been changed since the US 10 days. Since everything conflicts, I propose that we defer to signs and extend US 310 up to BL 90.