A swelling Auckland vehicle fleet is expected to be belching out at least one-fifth more carbon dioxide in 10 years' time.
The final draft of the region's land transport strategy, issued last week for public submissions before being adopted in December, forecasts a growth in Auckland car numbers from about 652,000 now to more than 830,000 in 2016.
This does not count vehicles owned by the more than 150,000 Aucklanders living outside the area covered by regional council computer modelling.
Although cleaner fuel and more efficient engines are expected to reduce pollutants such as nitrous oxide and diesel particulates, the strategy document forecasts a 21 per cent rise in carbon dioxide emissions - about 1500 tonnes in each morning traffic peak - even under the preferred strategic option that involves spending billions on public transport. This outlook clashes with the Government's national strategic target of a 20 per cent improvement in transport energy efficiency by 2012, the same year by when the Kyoto Protocol requires greenhouse gas emissions to be cut to 1990 levels.
Auckland Regional Land Transport Committee chairman Joel Cayford acknowledges that without curbing vehicle numbers, efforts to improve emission standards are akin to "rearranging deckchairs".
"New Zealand used to have the most washing machines per capita in the Western world - now it has the most cars," he says in his foreword to the transport strategy document.
"This year, polluted air from vehicle exhausts in Auckland will be directly responsible for more than 200 premature deaths."
The document forecasts a rise in the number of cars for every thousand urban Aucklanders to 609 in 2012 from about 570 now, statistics which Dr Cayford says puts the region well ahead of Los Angeles.
Christchurch City Council strategic planning leader Mark Bachels, a former Californian who gained a doctorate from comparing international transport trends, says New Zealand remains well behind the US in its levels of vehicle use - as opposed to the number of cars we own.
But he says this should give little cause for complacency, as increasing urban sprawl makes it harder to provide the level of public transport needed to discourage car use.
He notes strenuous efforts by Los Angeles authorities over the past 15 years to increase urban density and introduce passenger-rail transport.
Auckland Regional Council planners also draw a distinction between vehicle ownership and use, noting in the strategy document that although 646,000 private cars were registered in the region in 2001, only 334,000 were used each day to drive their owners to work.
The new strategy hopes to cut the proportion of commuters using cars to get to work to 73 per cent by 2016, while boosting public transport use from 7 to 11 per cent.
But after spending $420 millon on "travel demand management" to encourage non-vehicle transport, the number of people cycling or walking to work is expected to edge up just 0.4 of a percentage point, to 15.5 per cent.
* The draft Regional Land Transport Strategy can be viewed at www.arc.govt.nz
* Auckland's population is projected to grow by about 255,000 by 2016.
* By then the region's fuel use is likely to have increased 26 per cent.
* Statistics four years ago showed Auckland had an average of 1.66 cars for each household. Los Angeles had about 1.44.
* 78 per cent of Auckland commuters travelled by car to work but only 5 per cent went as passengers.
* The region's land transport strategy favours spending $3.75 billion on public transport over the 10 years compared with $6.54 billion on roads.