The incident occurred just before 2:30 p.m. Police say they can't confirm the vehicle's height or how hard it struck the overpass at Highway 10, also known as the Ladner Trunk Road.
However, the force of the impact was great enough to cause concern about the integrity of the overpass structure and crews were called to the scene to examine the damage.
Highway 99 southbound and Highway 10 eastbound are closed, particularly affecting commuters from downtown Vancouver and Richmond trying to reach Surrey, Delta, and White Rock.
Eastbound vehicles on Highway 10 are being detoured via Highway 99 southbound, northbound on Highway 91, rejoining Highway 10/Ladner Trunk Road.
Southbound traffic on Highway 99 is being detoured via the Highway 10/Ladner Trunk Road off-ramp, and rejoin Highway 99 southbound via the Highway 10/Ladner Trunk Road on-ramp.
Drive BC estimates Highway 99 may fully reopen between 8 p.m. and 11 p.m. PT. Deas Island RCMP says Highway 10 could fully reopen at 10 p.m. PT.