The inbound side of the Liberty Tunnel will close overnight Monday, according to the Pennsylvania Department of Transportation.
The tunnel will close to traffic from 8 p.m. Monday until 5 a.m. Tuesday.
Crews will begin work on a $3.5 million tunnel roof replacement project, PennDOT said in a news release.
Additional overnight closures and detours will occur as crews replace the roof this year but PennDOT said the tunnel is not expected to close in both directions at the same time.
The project — which also includes drainage improvements — is expected to wrap up late this year.
During the overnight closure, PennDOT recommended drivers detour to Route 51, known as Saw Mill Run Boulevard, northbound.
They can then take the left exit to Interstate 376 West/Route 19 South, then get off at Exit 69A toward 19 South/Banksville Road. The detour would then loop drivers back to I-376 East toward the Fort Pitt Tunnel and across the Fort Pitt Bridge.
