The section of barrier at Saddle Hill was damaged in a crash at the end of November.
NZ Transport Agency senior network manager Chris Harris said the agency was aiming to begin repairs on December 15.
The highway maintenance team was awaiting the arrival of essential parts from outside Dunedin, he said.
With supplier constraints in Auckland and fewer ferry sailings due to Covid-19 restrictions, the parts were taking longer to get to Otago than they would normally.
"We want to have this barrier replaced before Christmas and the higher traffic volume holiday period. But in the meantime, people should be alert and aware that there is no barrier protection from head-on crashes in that section of SH1."
The speed limit had been reduced to take into account of the lack of barrier through the section.
