The only road to Milford Sound is likely to re-open for around-the-clock use in February.
The Homer Tunnel linking Milford Sound to Te Anau in Fiordland has only been open between 7am and 7pm since December last year due to falling rocks.
The New Zealand Transport Agency is fitting a mesh rock shelter to try and direct falling rocks away from the road.
Southland area manager Peter Robinson says the shelter is a vital part in the plan to get the road safe for 24-hour use.
"The safety is the key element of what we're trying to achieve. The rockfall deflection will give a high level of safety to people travelling though there and will allow us then to work on the stuff above."
Mr Robinson says the first unit to the shelter was installed last week and the remaining four are due to be completed and installed by mid-February.