Traffic from southbound Route 51 (West Carson Street) will be unable to use the Corliss Tunnel starting at 7 a.m. Wednesday.
Vehicles won't be allowed to turn right onto Corliss Street as PennDOT reconstructs a manhole cover inside the Corliss Tunnel.
The work will continue around the clock through Oct. 4.
Here is the detour: Vehicles should continue past Corliss Street heading into the city, turn right onto Steuben Street, turn right onto Chartiers Avenue and turn right back onto Corliss Street.
Vehicles will be able to access southbound West Carson Street from Corliss Street.
The tunnel work is part of a $38.99 million project to replace a structurally deficient viaduct that supports part of Route 51 between the West End Circle and Stanhope Street.
Overall work will conclude in late summer 2015.
PennDOT is replacing a manhole cover inside the tunnel, meaning inbound traffic from West Carson Street can't turn right into the tunnel.