Documents detailing the effect of the proposed flyover on Wellington's public transport network were laid bare before a board of inquiry yesterday.
They predicted that, by 2021, buses will be able to get from Adelaide Rd to Cambridge Terrace a minute quicker than they do today during the 7am to 9am morning peak, given 1180 vehicles will be using the flyover instead of the Basin roundabout.
During the 4pm to 6pm evening peak, bus trips are forecast to be 40 seconds quicker.
One of the New Zealand Transport Agency's stated reasons for building a highway flyover, 20 metres north of the Basin, is to improve public transport.
Greater Wellington Regional Council transport planner Nick Sargent told the board that the flyover alone would not make a monumental difference in this area.
But with state highway traffic out of the equation, there would be enough room to eventually build dedicated bus lanes around the Basin roundabout, he said.
Those lanes, along with new rapid-transit buses, would shorten bus trips between the CBD and southeastern suburbs by between seven and 10 minutes.
Fellow council planner Andrew Campbell told the board that, even though the initial one-minute time saving sounded small, it could have big repercussions for ratepayers.
Knocking a minute off each service would allow the council to tighten up the bus schedule and potentially operate fewer peak-time buses, which cost $75,000 a year.
Mr Sargent said that currently about 36 per cent of all vehicle trips into the CBD from Kilbirnie and Newtown were on public transport.
With the bus rapid-transit network in place, that was expected to increase to 41 per cent by 2031.
When the board questioned whether that was particularly ambitious, Mr Sargent said it was considering driving would be a lot more attractive in 2031.
Cars were expected to be more fuel-efficient by then, and other roading projects such as Transmission Gully would have quickened the drive into Wellington city.
Board member James Baines asked whether a bus rapid-transit network could be built around the Basin without the flyover in place.
"Yes, it could be done," Mr Sargent replied. "But the accumulation of dis-benefits to other motorists would be so astronomical that I would be laughed out of anywhere I suggested it."
Public Transport Around the Basin
About 2000 public transport users traverse the Basin each morning (7am to 9am) on their way from the southern and eastern suburbs to the Wellington CBD.
They share that journey with about 5400 vehicles heading north and 1180 vehicles heading west on State Highway 1.
Average public transport travel speeds around the Basin during the morning peak are 20kmh northbound and 14kmh southbound.
Bus users' morning commute will be 60 seconds faster thanks to the Basin Reserve flyover.
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