The report which spurred Auckland Transport's decision to rule out heavy rail between the city centre and Auckland Airport is "deeply flawed" advocates say.

AT's board based its decision in June to drop trains as an option for a rapid and congestion-free network to the airport.

This followed an earlier decision by the New Zealand Transport Agency and cited a report saying trains could cost up to $1.3 billion more than trams, though both could reach the airport from downtown Auckland in around 40 minutes.

But at a meeting in Onehunga last night, advocates for "heavy rail" - like Auckland's new electric trains - said the report made fundamental assumptions that were incorrect.


Public transport advocacy group the Campaign for Better Transport's Graeme Easte said the report underestimated the cost of "light rail" (trams) from the CBD to the airport, as well as differences in travel time and passenger catchment areas.

He said the report only looked at the cost of a light rail link from Mt Roskill to the airport, and ignored the distance from the southern end of Dominion Rd to the CBD.

The report estimated travel time from Britomart to the airport via heavy rail at 39 to 42 minutes and via light rail at 42 and 44 minutes.

But Easte believed travel time for light rail was significantly underestimated.

"If light rail was to be used, it would be restricted to travelling at the same speed as traffic - 50km/h - 40 per cent of the way.

"We're not experts, but we think this is suspicious," he said.

He also believed passenger catchment analysis was flawed with light rail catchment including Sandringham Rd residents and heavy rail catchment excluding people using the western line who could link with trains to the airport.

"We want to see this report reviewed, rather than simply accepted," he said.

"There's an unfair screwing of the scrum, it would appear."

AT's chief strategy officer Peter Clark said the reason for the lower cost of light rail was that it could stay at road level the entire journey, rather than needing to be raised above traffic, as would heavy rail.

Auckland Airport's general manager of development, Graham Matthews, also present at the meeting, said the company anticipated visitor arrivals to increase from 17.3m this year to 40m by 2044.

Daily vehicle movements to the airport were 86,000 in December, and are estimated to increase to 174,000 by 2044.

"The bottom line for us is that we have to find an alternative means for getting people to the airport," he said.

The Airport needed a decision made on whether that would be light rail, heavy rail or bus, within the next year or two, as it planned a new terminal that would incorporate a station.