The cost of a cycle and walkway being built in Lower Hutt has doubled to $63m, or about $12m per kilometre.
The cost of the shared path between Petone and Melling train stations has doubled to $63m. Photo: Youtube / Waka Kotahi NZTA / Fair use
The blowout is revealed in board minutes.
Transport Agency Waka Kotahi said it was due to "multiple factors on site", but it did not spell out what those were.
The 5km-long path from Petone to Melling train station is the first part of Te Ara Tupua link into Wellington city, projected to cost more than $200m.
The path alongside the rail line was priced at $30m when work began in 2019. That then rose to $38.6m, and board minutes show Waka Kotahi has now approved putting in another $24.5m.
The blowout cuts the cost-benefit ratio in half from 1.2 to 0.6, and reduces the ratio for the whole of Te Ara Tupua from 1.0 to 0.9, the minutes show.
The shared path will next extend from Petone to Ngauranga.
"This route has been prioritised because it enables a shift towards walking and cycling and a reduction in transport emissions by fixing a missing link in the region's cycling network," the agency said.