Wellington motorists face months of delays with quake-strengthening of the Karori tunnel beginning this week.
The tunnel will operate as normal between 7am-9.30am and 3pm-7pm, but be confined to one lane at other times from Monday through to Saturday with temporary signals in place.
Sunday work is also possible, and the tunnel may also sometimes close overnight and briefly during the middle of the day. The work is expected to be completed by November.
Wellington City Council warns that there will be delays at times and motorists should consider alternative routes.
Council infrastructure director Stavros Michael says motorists should add 10 minutes to their travel time.
He warns the work will be noisy at times.
The tunnel is near the city's main fault line and while assessments show it is likely to withstand a large earthquake, its entrances are vulnerable and the adjacent hill on the city side is prone to slips.
Both entrances are being rebuilt and a new concrete retaining wall is being constructed along Glenmore Street on the Kelburn side of the tunnel.
Trolley bus wires will be disconnected, with diesel buses operating to Karori until the work is completed.
Wellington City Councillor Andy Foster says the project is important to help strengthen and protect the city's main transport routes.
The council has already done major strengthening work in Ngaio Gorge Road on an alternative route out of the city, and future work is planned on Churchill Drive, the Hataitai bus tunnel and the Seatoun and Northland tunnels.
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