The road ahead for Let's Get Wellington Moving is becoming increasingly unclear with NZTA officials confirming potential for the project to be "rejigged".
A Transport and Infrastructure select committee has also heard official advice was to build a second Mt Victoria tunnel "sooner rather than later", the opposite timing Cabinet's signed off on.
NZTA's incoming chair and interim chief executive were among those hauled in for questioning by the select committee today.
The $6.4b LGWM transport plan has copped criticism for being light on detail, with detailed business cases yet to be undertaken.
It puts mass rapid transit front and centre, but roading projects like a second Terrace tunnel and trenching Karo Drive have been turfed.
When questioned by National's Transport spokesman Chris Bishop, NZTA's interim chief executive Mark Ratcliffe said the final elements of the package were decided by ministers and local elected officials.
He said NZTA did not have a role in that.
"I'm newish to the transport game but I think at the end of the day it's leaving the priorities there. We are largely a delivery vehicle."
NZTA's incoming chair Brian Roche said if the business cases did not stack up, then they would not proceed and the programme would have to be 'rejigged'.
"The programme as it's announced is a commitment to address a number of issues in Wellington.
"It is also indicative of a number of the solutions that we collectively think are possible so it's more than aspirational but it's not signed off and I don't think there's been anything that says this is what we're definitely going to do."
National list MP Nicola Willis also questioned officials in the select committee.
They confirmed advice for a second Mt Victoria tunnel was to build it "sooner rather than later".
But the programme being worked towards was based on the LGWM Cabinet paper, which directed the timing of the tunnel to be "later rather than sooner".
When asked why that was, LGWM programme director Andrew Body said it was a question for the Transport Minister.
The advice said the downsides of removing or delaying a second tunnel would result in poor quality walking and cycling connections, unreliable traffic times, and would add to pressure arising from the construction of mass rapid transit.
Willis said she was concerned NZTA was not able to influence the package to ensure it was as effective as possible.
"It looks like we're now in a situation where ministers ignore the advice of the Transport Authority and just cherry-pick projects based on their whims.
"It's an absolute gutting of NZTA's role if all they're there to do is to deliver on ministers' ideas."
Associate Transport Minister Julie Anne Genter said that was not true.
"We took advice from the NZTA and from the project team and ultimately Cabinet made a decision that reflected the prioritisation of public transport, which is what came out loud and clear from the consultation."