NZ Transport Agency's preferred Welcome Bay underpass option is the one that will cause the most disruption for nearby residents.

A concept plan of the preferred option.

While the details are not set in stone, NZTA senior project manager Andrew Scott says their preferred option might require the purchase of several Hammond Street properties and the Welcome Bay scout hall across the stream.

A tighter design will be available by the end of the month, which will be enough to start off the Resource Management Act process.

'The outcome of this will determine which houses are affected or not.”

That process usually takes 9-24 months.

NZTA and BECA staff were at the Tauranga City Council's Ten Year Plan meeting today to answer questions raised by councillors about the Welcome Bay underpass.

Councillor Bill Grainger wanted to know why the traffic lights option was preferred by NZTA when the roundabout options provide better access for Ohauiti traffic.

Andrew says the underpass options are concept designs which assist NZTA in making the choice about the underpass, instead of a roundabout, overpass or gyratory.

The traffic lights option provides better answers to questions about connections for Welcome Bay traffic and Hammond Street; traffic lights are also more pedestrian and cycle friendly.

'Pedestrian and cyclist access is not that great through a roundabout,” says Andrew.

'Placing a roundabout down the hill from the underpass places the roundabout on a slope, which is not preferred.”

Access to the roundabout would be too steep down the hill from Ohauiti, and the traffic lights option means they can move it far enough away to work properly.

'The traffic lights can balance the traffic flow and the slip lane provides free flow onto State Highway 29 for Welcome Bay traffic turning towards Greerton,” says Andrew.

Network issues haven't yet been worked through.

These include the merging of Tauranga bound traffic, which with the underpass lane, Hairini Street and the lane from the Maungatapu roundabout, will be three lanes.

Hairini Street could get blocked off or become a bus only lane, says Andrew.

They are the kind of issues that will be discussed with city council staff in the project's next stage.

'That sort of discussion is a couple of years away,” says Andrew.

'That level of detail is not where we are at the moment.”

The councillors endorsed the option, noting that the timing and funding of both stages three and four of the Hairini Link will be considered by NZTA and TCC.

Mayor Stuart Crosby says regular updates to the city council can be made via the council's projects and monitoring committee.