Although it opened briefly at one point, it has been closed permanently since last May.
Mr Cavanagh, a member of the residents' association, believes it's the first time a government agency has agreed to carry out an independent review at its own cost on behalf of an affected community. The cost of the peer review is estimated to be $10,000.
However he's suspicious a decision not to open the on-ramp has been pre-determined and the result will be an excuse for Transport Minister Steven Joyce to sign off the on-ramp's permanent closure.
Mr Cavanagh described two meetings with NZTA about a month ago where it was asked to consider an independent peer review. He said it took four weeks before traffic engineer Wesley Edwards was signed up to head it. Mr Cavanagh asked the agency whether it would be prepared to reopen the on-ramp.
"They wouldn't give an answer and wouldn't say why.
"We've had no information about the scope of the review. They're keeping everything close to their chests, yet they have a statutory obligation to be transparent. Until Wesley Edwards reports progress, I'm concerned."
He claims the agency is deliberately slowing progress so the public can be presented with a "fait accompli".
"They know how to run these things. They have to be seen to approach consultation with an open mind. A state organisation has the facilities to build its case but for others to respond it's incredibly expensive."
Mr Cavanagh says it isn't possible to properly evaluate whether to open the on-ramp without a trial reopening.
"We're concerned there's no indication they are seriously considering the possibility of reopening. We need to see what's being done."
He suspects the transport agency is reluctant to reopen the on-ramp in case the community is proved right. "They know if they open it and it works, they'll never get it closed."
AUTOMOBILE ASSOCIATION BACKING
AA's Auckland spokesperson, Simon Lambourne, says the on-ramp closure limits access to the motorway, underuses valuable infrastructure and causes congestion.
"If NZTA wished to consult the public about a permanent closure, then it should have done so only once it had fulfilled its commitment by reopening the on-ramp."
Mr Lambourne says claims that the on-ramp needs to stay closed to collect traffic data from local roads are "nonsensical".
"Such data should have been collected during the Victoria Park Tunnel construction and a failure to do so shows a lack of planning."
The AA is concerned the agency's "unsound" logic indicates a preference for fewer on-ramps to prioritise through-traffic. The residents' association agrees, and says "the closure of the Wellington St on-ramp is, in traffic engineering terms, deeply flawed".
Mr Lambourne says the construction of the tunnel gives little thought to how traffic can merge safely - which seems to be repeating problems associated with the performance of the Manukau Interchange. He says AA is concerned about the technical advice the agency is receiving.
He says the permanent closure of the on-ramp rests on the ability of Curran and Fanshawe streets to carry and feed the estimated 7000 extra vehicles that would normally use the on-ramp on to the Harbour Bridge. "This is unworkable due to the physical limitations of both roads."
The AA explains: "Curran St in Herne Bay is unique as an extremely narrow, two-lane feeder access to ... the Harbour Bridge. While it's described in the Auckland City Plan as a regional arterial road, it is just over 10m wide and well short of the 20m minimum specified in the plan. It's also purely residential in composition and includes a major school - Ponsonby Primary School. Carrying excess traffic volumes due to the closure of the on-ramp, as well as heavy traffic, is not feasible.
"In the case of Fanshawe St ... NZTA has spent millions of dollars reconfiguring it to produce a two-lane entry to the Harbour Bridge. Since the closure of the on-ramp, increased volumes of traffic building on both Beaumont and Fanshawe streets has caused significant congestion with 'rat running' through Ponsonby to the Curran St on-ramp."
In April, The Aucklander talked to Beaumont St residents who said the increase in traffic in their street was causing problems.
In May, Auckland Council's transport committee said it supported residents' bid to have the on-ramp reopened.
Councillor Mike Lee, the committee chair, said: "It's been there for several decades and driver habits have grown around it. It's been paid for by taxpayers and it'd be wasteful to close it and unfair on ratepayers. We didn't build the on-ramp, NZTA did - but it's now part of amenities and we need it opened again."
Public submissions closed on July 13 and more than 700 were received. The NZTA's Auckland regional director, Stephen Town, says the level of support for reopening or keeping the on-ramp closed will be released when NZTA and Auckland Transport have completed their analysis of the feedback.
"We're now working through those responses," Mr Town says.
"Together with technical data relating to motorway and local road traffic we are gathering, the views of Aucklanders will help form our proposal for the future use of the on-ramp."
The proposal will then be peer reviewed before community groups are contacted in August.
But he said whatever happens, there would be a trial reopening.
"If it is proposed that the on-ramp should be closed permanently, the NZTA would make no final decision without first re-opening the on-ramp on a trial basis to analyse its impact on traffic and ensure that the decision would be the correct one."
What do you think? Have your say in the comment box below. Or head to our Facebook page.