Government plans for a $2.2 billion light rail project to West Auckland go against a business case that says a busway can be built relatively quickly and cheaply.
Light rail, a modern-day version of trams, came second behind the preferred option of a busway in an indicative business case for rapid transit to northwest Auckland.
Rail was looked at, but found to be very expensive at about $4b, difficult to stage and complex to integrate with the existing rail system out west.
The business case, obtained by the Herald under the Official Information Act, said light rail would have to be built in one package, whereas a busway can be staged.
It said the busway was designed to light rail standards and could be upgraded to light rail in the final stage of the programme.
"Buses can easily move on and off the busway, and also use the motorway, bus lanes and regular streets," said the business case, prepared for Auckland Transport by consultants Aurecon New Zealand Ltd and MRCagney.
Since the business case was completed in July last year, Labour has been elected on a promise to build two lights rail lines from the CBD to the airport and Westgate within 10 years, costing $6b. The business case talked about a solution over multiple decades.
Twyford said Labour was going straight to light rail to avoid the cost and hassle of building a busway first.
"To cope with population growth, we would need to replace the busway with light rail in time because light rail can carry more people than a busway.
"We don't want to disrupt one of the city's major arteries again in 15 or so years. Better to do it once and do it right," he said.
Twyford said the indicative business case did not properly consider the intensification benefits of light rail or the disruption of replacing busway in the future.
New Zealand Transport Agency chief executive Fergus Gammie has told the Herald the plan for trams from the CBD to Westgate will probably be extended to Kumeu.
No costings are believed to have been done for light rail to Kumeu, but the business case said light rail is more expensive and difficult than busways to extend beyond Westgate into growth areas.
The business case said light rail is the best option in achieving transport outcomes, but may not be required for some time and has many risks that bus-based solutions can avoid, particularly the need to build across the causeway alongside the northwestern motorway.
Both options face environmental challenges. The causeway is adjacent to Traherne Island and Pollen Island marine reserve, a new bridge over the Whau River is within a special ecological area, and habitat loss is expected in Oakley Creek.
The options could also see the loss of six pohutukawa trees opposite Motat on Great North Rd that were saved from the chop after a public outcry during work to widen the northwestern motorway.
The busway was costed at $2b and light rail, via State Highway 16, at $2.2b.
Twyford said the Government is building transport infrastructure that can cope with future growth, rather than constantly playing catch-up like we have for the past 30 years.
"Light rail is a powerful stimulus for growth. Light rail from the CBD to the Northwest will enable redevelopment and intensification along the whole route, including the KiwiBuild development at Unitec, without adding more congestion to the roads," he said.
Waitakere councillor Linda Cooper said 10 years was too long for West Aucklanders to wait for light rail by which time there would be another 40,000 people living out west.
"For people in West Auckland, they are feeling left out. They will be paying the fuel tax, it does affect people on lower incomes and if they knew they were getting something a bit quicker it might help take the sting out of that," she said.
Cooper said trams worked well in built-up suburban areas like Dominion Rd where people can walk to a station, but there were no suburban areas along the northwestern motorway where light rail will be built.
People would need to get a bus or drive to light rail, said Cooper.
"It's not the right mode for the location," she said.