Motorists travelling from Ngauranga to the Hutt Valley are in for about four months of potential delays as the NZ Transport Agency upgrades the State Highway 2 on-ramp.
From mid-February, the agency will be extending the double-lane section of the northbound on-ramp, installing new roadside barriers and pavement markings, and improving the merge area with SH2.
Weather permitting, the work should be finished by June.
Until then, traffic management measures will be in place at the merge point where traffic travelling from the Ngauranga Gorge towards Petone joins SH2 just north of the interchange.
Most of the work will be done during the day, but a section at the end of the ramp will be worked on at night. All works will be behind concrete barriers and separate from traffic.
Wellington state highways manager Rod James asked motorists to take extra care during the construction period and allow a few extra minutes for their journeys.
Any delays were likely to be minor, he said.
The changes may end up looking ''relatively subtle'' but they were expected to make a noticeable improvement to how traffic flows at the very busy on-ramp, he said.
''The biggest difference will be for people travelling home towards the Hutt Valley during the evening rush hour from both Ngauranga and Wellington, easing the current queues and improving the safety of the merge.''
Between 11,000 and 13,000 cars use the merge lane every day, out of an estimated 80,000 to 90,000 that use the interchange.
The work is part of Stage 1 of the agency's Ngauranga to Aotea Quay project, which is costing the agency $3.9 million.
It follows on from improvements to the Ngauranga Interchange where SH1 and SH2 traffic both merges and separates. That work was completed in August 2011.
The Ngauranga to Aotea Quay project is part of the Wellington Northern Corridor road of national significance, which runs from Levin to Wellington Airport.
- The Dominion Post
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