The cost of Tauranga's short but pricey Baypark to Bayfair highway link has risen by another $30m to almost $300m.
The 1.7km stretch is shaping up as one of the most expensive and longest-running ever of highway projects.
The new forecast of $292m is up from $262m a year ago, almost three times the original 2015 estimate, and twice what it was put at in 2020.
Waka Kotahi said it was still on target to open late this year.
It was "seeing cost increases continue across all projects", it said.
The NZ Transport Agency regional manager of infrastructure delivery Jo Wilton said like the rest of New Zealand and other parts of the world, Covid has had long lasting consequences.
"Projects in the Bay of Plenty continue to be affected by the challenges resulting from the ongoing impacts of Covid-19, including a constrained labour market, supply chain issues and cost escalations," she said.
"We are working closely with our suppliers and contractors to achieve greater efficiencies."
The original design failed to account for softer than expected ground conditions, especially a section of buried pumice 300m long that was impractical to dig out.