Get Moving: Dips in bridge are legacy of work done decades ago

Q. When crossing the Upper Harbour Bridge at Greenhithe, you get the impression that the deck sags between the piles. Can this possibly be so? Will the old bridge be closed when the new one opens? Will the new expressway overpass Brighams Creek Rd? W. Martin, Milford

A. There is a slight dip between the piers of the bridge. It happened when the bridge was being built 30-odd years ago, and was caused by tensioning cables used to compact the concrete. Transit says it has no structural significance, which is a good thing. The old bridge will not close when the new one opens. It will carry two lanes of traffic downhill, while the new one will carry three lanes uphill. And a big interchange is planned for Brighams Creek.

Q. What are the two parallel blue lines about the same distance apart as a car's wheels, following the middle of the slow lane at the end of the Northern Motorway just before Orewa? Nick Smith, Auckland.

A. The blue lines mark out what are known as pavement calibration sites. Lasers mounted on high-speed survey vehicles measure the condition of the road surface each year in the same places, to check for roughness, rutting and texture. There are a number of such sites around the country, some of them marked by white dotted lines instead of blue.

Q. Last year, half of Hall Ave in Mangere was resurfaced. Can you tell me when the other half of the job will be completed? Stephen Millham, Mangere.

A. The job was due to be finished in 2006, but the project has been delayed and is now scheduled to be done during the 2006-2007 financial year.

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Contact Phoebe Falconer at Get Moving, editorial department, NZ Herald, PO Box 32, Auckland. Fax (09) 373-6421 or email the newsdesk (see below for link). Include name and address.