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Auckland's public transport agency is offering a down-payment on the "holy grail" of a possible rail link between the airport and Britomart.
The Auckland Regional Transport Authority has offered to pay Transit NZ up to $2.5 million to "future-proof" its duplicate motorway crossing of Manukau harbour "to accommodate a passenger rail connection."
Transit, which has obtained resource consents but still faces appeals against the $265 million roading project, has indicated its readiness to make some of the foundations and piers of a duplicate bridge strong enough to carry a rail line most of the way across the harbour between Onehunga and Mangere.
One of two options shortlisted by the transport authority involves building a separate railway bridge to the west of the motorway, but the other envisages running trains beneath it, sharing some - although not all - of its piers.
Because the railway line would deviate from the motorway on each shore of the harbour, engineering consultants say it would need to share just three of the new bridge's eight sets of piers.
They believe it would cost between $1.5 million and $2.5 million to future-proof the bridge to that extent - compared with an estimate by Transit of up to $20 million for making its foundations strong enough to carry a cantilevered railway line to the east of the motorway.
The transport authority has therefore asked Transit to accept the compromise proposal, subject to developing a funding strategy with its parent body the Auckland Regional Council and with Government rail agency Ontrack.
A shared structure would be mainly within Transit's existing bridge designation and would be more acceptable to the local community instead of a separate bridge to the west.
Running it to the east would mean having to build a railway bridge across the motorway at some point further south.
Regional council chairman Mike Lee said the transport authority's decision was crucial to ensuring that those needing to get to the airport for work or to catch flights were not doomed to an increasingly congested roads-only future.
