Auckland's Northern Busway is being hailed in a Transport Agency report as a major growth stimulant for the central business district.
The report by agency consultants says the busway is largely responsible for a 15 per cent increase in those crossing the harbour bridge, which would become substantially more congested without the $300 million facility.
An estimated 43 per cent of the approximately 7500 passengers who crossed the bridge on buses in morning peak periods in 2010 were believed to have been former car commuters, making buses responsible for 33.1 per cent of travel from North Shore to the city.
Labour transport spokesman Phil Twyford, who obtained the report ahead of publication, said it showed the busway had been a remarkable success and would add weight to a campaign for a similar public transport highway from West Auckland.
"It has prevented total gridlock on the bridge and Northern Motorway," he said yesterday.
Mr Twyford, the MP for Te Atatu, said it showed that the best thing the Transport Agency could do to keep traffic moving along state highways was to invest in pubic transport.
"The success of the Northern Busway is delaying the spending of billions of dollars on the second harbour crossing," he said.
"Likewise the [$2.86 billion tunnelled] City Rail Link and things like the North West Busway are the best and cheapest way to stop Spaghetti Junction clogging to a standstill from the extra traffic that will be delivered by the widening of State Highway 16 and the developments in the northwest and SH20."
He was referring to the $2 billion Waterfront motorway projects and the development of a new town centre north of Westgate.
The Transport Agency said bus patronage from North Shore to central Auckland grew by 81 per cent between 2001 and 2011, well above predictions.