The 401 will be closed in both directions this weekend just west of London.
The shut down will close the highway from Iona Road to Colonel Talbot Road and it will start Saturday at 9 p.m. and will last until Sunday at 9 a.m.
Construction crews will be demolishing the east half of the Union Road underpass.
Traffic will be rerouted at Iona Road and Colonel Talbot.
Motorists should expect delays.