Porter Street in Templestowe will be closed at Fitzsimons Lane on Wednesday for a month, requiring a major detour.
Work on the notoriously scary roundabout is part of the Fitzsimons Lane upgrade that is improving a number of intersections along the route.
Hawtin Street and Edwin Road will also be closed at Porter Street.
Local traffic will be able to access Templestowe Reserve and BlueCross Aged Care from the Warrandyte direction.
Formal detours for all traffic will be in place using Foote Street, Reynolds Road, Blackburn Road and Warrandyte Road.
Riders with local knowledge may have better solutions.