A new fire protection system is being installed in Lyttelton Tunnel.
The work kept the tunnel closed Sunday night. It will remain closed Monday and Tuesday from 11pm to 4am the next morning.
The tunnel will open for 10 minutes each hour on each of the three nights to allow the traffic though.
The $28.7 million plan is expected to be complete next year.
This is the first of many closures that will occur in the coming months.