The New Zealand Transport Agency's overnight maintenance work in the Lyttelton Tunnel will continue for another week.
NZTA Journey Manager Lee Wright said the Agency had three different projects underway in the Lyttelton Tunnel this month.
These included the replacement of the centre line smart studs (illuminated cat's eyes) for the full length of the tunnel.
Contractors will also clean and replace the tunnel lighting, and install air-quality monitoring equipment.
The work is essential, and will take place from 9pm to 6am, starting tonight and ending on Saturday morning, July 16.