Ask Phoebe: Causeway trial will test effect of new road on marine life

Motu Manawa - Pollen Island Marine Reserve. Photo / Supplied

What is being built out in the tide next to the Northwestern Motorway between Patiki Rd and Waterview? Brian Boys, West Auckland.

I apologise for my somewhat peremptory answer last time, Mr Boys. Here's what the Transport Agency has to say.

The work behind the screens on SH16 (east of the Rosebank onramp) is part of a trial connected with its plans to raise and widen this section of the Northwestern Motorway as it develops the Western Ring Route. The causeway passes through the Motu Manawa-Pollen Island Marine Reserve and the trial will provide design, and environmental information to help the agency decide the best way to upgrade this section of motorway in an environmentally sensitive area.

The trial includes construction of a 50m temporary causeway, which is 1.5m higher than the adjacent motorway. During the $6 million trial - which started in January and is due to finish in August - marine life in the reserve is being monitored. Construction of the 4.2km causeway upgrade between Waterview and Te Atatu is expected to start next year.

The $270 million project also includes upgrading the Rosebank and Patiki interchanges, providing treatment to stormwater runoff, widening bridges and improving the Northwestern cycleway and pedestrian facilities along the route. It is expected to be completed in 2017.

At the Gillies Ave offramp southbound, there are two lanes for traffic turning right into Gillies Ave. Painted on the road on the side of the right hand lane is a solid white line, which continues down the off ramp and turns round into Gillies Ave, in front of the overbridge support. To someone who has followed lane markings on the motorway for some distance and especially at night, this line can be quite misleading. I have followed it round into Gillies Ave and ended up on the wrong side of the road, and my husband and I have followed other cars making the same mistake. A week or two back we followed a car that returned to the left hand side of the road only when the driver saw the headlights of an oncoming car. There is a guide line across the intersection to assist drivers in the other right turning lane to make the right hand turn but at night this appears to merge into the yellow centreline, creating the illusion that both sides of the road under the bridge are for the right turning traffic. Better road marking is needed. Joan Wilson, Auckland.

I went for a look, and it's my understanding that the solid white line on your right is there to delineate the edge of the roadway. The path you should take is to follow the dashed white line on your left, which will guide you into the correct lane on Gillies Ave.

* I was misled by a question last week concerning the St Marks motorway onramp. There is no longer a give way sign on the Newmarket side of the onramp, although faded road markings indicate that there was previously. The give way sign at the beginning of the onramp on the Remuera side means that traffic coming from Newmarket has right of way.

I apologise for the confusion. I have learned from it.