KEY POINTS:
Car-pooling should leave a smaller carbon "footprint" than buses over Auckland Harbour Bridge, says a businessman seeking access to the Northern Busway for vehicles with three or more occupants.
Paul Minett of Trip Convergence Ltd says car-pooling would prove at least as green an option for North Shore commuters, once the carbon dioxide output of high-occupancy vehicles was measured against average bus patronage over a full day.
Although Transit NZ has planning approval to let up to 350 high-occupancy cars an hour use the new $300 million busway - as well as 250 buses - it fears that may compromise efficient operations before a motorway bottleneck on the Auckland side of the bridge can be eased.
It says cars merging with general traffic after leaving the busway would have great difficulty crossing into southbound lanes near the motorway's Fanshawe St exit, until a tunnel opens under Victoria Park in 2013.
But Mr Minett says road congestion is too serious a problem for Transit not to seize an early opportunity to remove 1000 cars an hour from the motorway system in peak morning traffic, even if the busway has to be restricted to traffic bound for central Auckland, and no further south.
He pointed yesterday to a busway on-ramp built at the Constellation Drive bus station especially for high-occupancy vehicles.
He said his company was prepared to manage this on Transit's behalf as part of a high-tech car-pooling scheme which would be more flexible than traditional ride-sharing arrangements.
Participants with infra-red activating cards would form car pools at a series of parking stations between Constellation Drive and Silverdale, where they would choose whether to offer lifts to fellow members of the scheme or to ride as passengers.
An electronic tag on cars would record who was travelling in them, then automatically deduct ride "credits" from passengers or add credits to drivers' accounts.
Mr Minett said that would allow vehicles to be loaded as quickly as on taxi ranks, without obliging participants to be in the same place at the same time every day, which was a drawback of traditional car-pooling.
Although a sole-occupant Herald car is estimated to have pumped six times more carbon dioxide into the atmosphere than a reporter riding a crowded bus from Campbells Bay to Auckland, Mr Minett said the environmental scales would have been more balanced in a comparison of car-pooling with daily bus patronage.
He said that the bus passenger's carbon "footprint" should have been doubled in the Herald's experiment to allow for a return trip by a virtually empty bus, and the car's output divided by three.
"You should give reference to the fact that a car with three people in it would be as green as the bus," he said.
The Herald yesterday calculated the average carbon output of 17,969 passengers reported by the Auckland Regional Authority to have caught the busway's dedicated Northern Express service last week at various points on the 17.5km journey from Albany to Britomart - a 48 per cent increase from a year ago.
It worked out at an average of 970g of carbon dioxide for each passenger over the 1318 trips made between Monday and Sunday.
The figures are based on Ritchies Transport's estimate of typical fuel consumption for the modern Scania buses it uses solely for the express service, which includes the 6.2km busway.
By comparison, three people travelling from Albany in the same 1500cc Hyundai car used for the Campbells Bay trip would each have generated 893g of carbon, according to an estimate based on the manufacturer's fuel rating.
Occupants of a 1500cc Toyota Prius hybrid petrol-electric car would have each generated 586g of carbon, compared with 1.733kg contributed by those travelling in a 4000cc Ford Territory four-wheel-drive.
CARBON FOOTPRINTS
* Between Albany bus station and Britomart (distance 17.5km)
* Northern Express bus (based on weekly patronage) - 970g per passenger
* Hyundai Accent 1500cc car - 893g per occupant
* Toyota Prius 1500cc petrol-electric car - 586g per occupant
* Ford Territory 4000cc four-wheel-drive - 1.733kg per occupant
