Fulton and Hogan last year started the $3.1 million road safety project in Oamaru aimed at reducing the number of crashes - about 20 a year - between the Severn-Thames-Coquet Sts and Ouse-Thames Sts intersections on SH1.
The project, which also involved shifting the Boer War monument, was to be completed in April.
However, the completion date is now about two weeks longer with the authority deciding to do extra maintenance work in conjunction with the project rather than come back in a year or two.
Regional projects manager Simon Underwood said yesterday the additional work involved reshaping and strengthening the highway pavement between the Severn and Dee Sts intersections.
Addition reshaping and strengthening work would be carried out as far north as Usk St.
Mr Underwood said the road safety project initially involved the intersections, where traffic lights were being installed, some to replace roundabouts.
But the authority found the pavement between the intersections also needed maintenance work and decided to do that at the same time as the major project.
"Probably that [extra] work would need to be done within two years, and we did not want to come back and cause further disruption.
"It will also result in a higher quality and smooth surface," he said.
Most work would be completed by April, with the commissioning of the new traffic lights expected towards the end of that month or early May after road marking was completed.
It meant a ceremony to mark completion of the project and re-establishment of the Boer War monument would now take place about mid-May instead of before Anzac Day as originally planned.
This week, work is focused on the Severn-Thames-Coquet Sts intersection, including kerbing and channelling.
Further work, including wiring, will be done on the traffic lights.
Other work planned this month includes installing cobblestones on the west side of Thames St between Ribble and Coquet Sts, constructing the raised intersection platform at Coquet St and preparing the centre median for replanting the Siberian elm trees.
