Work on the $6.4 million upgrade to the intersection between Tucker Beach Rd and State Highway 6, near Frankton, started in September.
When the project was first announced in May, the NZ Transport Agency hoped to have it completed by Christmas.
However, in August it announced the slip road, accessed via an underpass beneath the Lower Shotover bridge, had been delayed until at least February.
This week NZTA senior project manager Phil Dowsett said the opening of the "ramp/underpass" was one of the last activities in the programme of works "so that may not occur until April".
"In order for it to be safely opened it requires all its safety features to be in place, [for example] road markings, signs, crash barriers and street lighting.
"Therefore, there is little left to be done after that other than landscaping and tidying the site."
Mr Dowsett said existing traffic management restrictions would be "wound back" before Christmas to help ensure state highway traffic flowed as smoothly as possible over the peak summer holiday period.
Since work started on the site in September traffic jams, particularly for peak morning commuters heading towards Queenstown and Frankton, have been a daily occurrence.
At present, Tucker Beach Rd is left-turn in and out only.
Temporary speed limits and traffic cones are also in place as contractors work on the slip lane, being created on what was an unofficial hard shoulder, or slow lane.
Mr Dowsett said Downer, which had brought "significant resources" to the site, would resume work in early January.
To date, Queenstown Lakes District Council wastewater pipes had been buried along most of the route on the State Highway and the polyethylene watermain pipe had been welded into a continuous length.
It was sitting on the surface ready for trenching this week.
The majority of existing underground services had been relocated clear of the slip road on the highway embankment and excavation had started for foundations of the "mechanically-stabilised earth retaining wall" which would support the slip road.
Work was also starting on widening the connection from Tucker Beach Rd to the slip road under the bridge, he said.
The contract value was "tracking close to what was expected," Mr Dowsett said.
