Squeezing more from motorway corridors

All this week we are featuring multi-million-dollar improvements planned for Auckland's congested motorway system.

The Auckland region's road system has not kept pace with the growth of population and traffic in the last two decades.

The 30km of Southern Motorway from downtown Auckland to Papakura is now heavily congested. The morning peak starts at around 7.30 and continues until 10. The evening peak extends from 3 to 7.

The morning traffic includes the 40 per cent of all traffic said to be travelling to school and other educational facilities that abound in central Auckland.

In the evening the northbound slow-moving tail trying to get through Spaghetti Junction is often back at Ellerslie Penrose by mid-afternoon.

And evening traffic going south is often reduced to a crawl as well.

Here are some of the projects being built or planned for the Southern in the next 10 years. They reflect an effort to get more traffic capacity into a restricted corridor. And the need to update the way the motorway is handled, so more traffic flows.

Each project involves extensive consultation with local bodies, local people and others affected.

And the Government's land transport funding agency Land Transport NZ (formerly Transfund) has to agree to provide the money.

Sometimes motorway work will also mean changes to local council arterial roads.

1 and 2. Central motorway junction and Grafton Gully

The $195.4 million central motorway projects in Spaghetti Junction involve important new motorway to motorway links, including between the Northwest and Northern both ways.

Also direct motorway links to the Port of Auckland through the already completed $68 million Grafton Gully project. And there will be improved links between the Southern and Northwestern.

New, safer on-ramps and off-ramps are being installed in the central city and additional lanes allowing citybound and through motorway traffic to be kept apart. Junction project finish 2006-07.

3. Newmarket viaduct upgrade

Options still being studied. The present viaduct structure, opened in 1966, is now rated inadequate. It was also built to stand a once-in-500-year magnitude earthquake, while modern standards stipulate 2500 to 5000 years.

The present six viaduct traffic lanes need to be seven, allowing another southbound lane.

Newmarket viaduct options include a new structure alongside the present viaduct, gradually replacing the old structure - but of necessity keeping a 200,000 vehicles-a-day route through the area open while the work is done.

A new structure is expected to require further new land designation adjacent to the present viaduct. Earliest construction start 2007-08 with 2010-11 finish. Cost around $85 million.

4. Newmarket viaduct to Greenlane auxiliary lane

Aims to provide four southbound lanes to match the four southbound planned from a revamped Newmarket viaduct.

The two outer (eastern) lanes would exit into the Greenlane roundabout. The motorway sheds a lot of southbound traffic at Greenlane.

The two inner (western) lanes would be for southbound through traffic. Still under investigation. Cost $20 million, Completion target 2009-10.

5. Greenlane east interchange

A big improvement being planned with Auckland City, allowing traffic travelling on Greenlane East and West roads to go straight through the interchange, free of traffic going to motorway on-ramps. Also free turns and better merging for motorway traffic. Some bus lane improvements also planned. Construction planned 2005-06 costing about $2.4 million.

6. Ellerslie-Panmure highway interchange to Greenlane East interchange

Extend the present northbound auxiliary lane which exits at Greenlane East.

It would be lengthened southwards, all the way back to Ellerslie-Panmure interchange on-ramp. Aim is to ease peak congestion. Still under investigation. No date set.

7. Ellerslie-Panmure highway interchange

Southbound offramp from motorway to get a left turn slip lane which motorway traffic can use without giving way. Safety change from present give way arrangement which has restricted vision. Cost $170,000. Finished by end 2005.

8. Southeastern highway to Ellerslie, northbound auxiliary lane*

Needed to ease congestion at this peak hour bottleneck created where the newish Southeastern arterial road has a short merge with northbound Southern Motorway traffic. Will allow a much more gradual merge and should help traffic wishing to exit at Ellerslie. Cost $8.2 million. No date set.

9. Mt Wellington off-ramp

This off-ramp northbound is to get a left-turn slip lane costing $2.2 million aimed at easing congestion. Construction aim 2006-07.

10. Mt Wellington interchange bypass*

This is a $100,000 bus priority lane. The busy Mt Wellington interchange is close to the very big retail and apartment development planned at Sylvia Park.

Improvements to the local road network including the Mt Wellington Highway are planned by Auckland City and expected to cope with the extra traffic. The development is also right by a rail station due for upgrading in 2007-08.

11. Otahuhu to Waiouru four-laning

As part of the work installing the new Waiouru interchange the Southern Motorway will get a fourth lane each way - from Princes St, Otahuhu, southbound to the new interchange north of Bairds Rd. And northbound from the Waiouru link to the Water St, Otahuhu, off-ramp.

12. Waiouru connection interchange

A $20 million project just starting with completion 2007-08. Part of a Transfund assisted $66 million joint Transit NZ-Manukau City project. It will connect the Waiouru Peninsula (including a new business park) with the Southern Motorway just north of the Bairds Rd bridge over the motorway.

13. Hill Rd Manurewa to Takanini three-laning*

Extra southbound lane, giving three traffic lanes to match the three northbound already done. Cost $6.7 million. No date.

14. Takanini interchange upgrade*

Expected cost $3 million. An old interchange, originally serving largely country area. At present has very short merge with northbound traffic. No date.

15. Takanini to Papakura six-laning*

Widened from two to three lanes each way. Cost $7.4 million. No date.

16. Papakura interchange upgrade*

Cost $10.3 million. No date. Interchange now getting heavier use through growth in Papakura-Franklin area.

* Projects marked * could be built sooner than otherwise expected through injections of extra cash from the new 5.6c-a-litre petrol tax and road-user charges for light diesel vehicles expected.

This tax is expected to feed about $207 million a year into a Regional Development Fund from about April.

Given recent sharp rises in oil prices a final Government decision is still awaited. The intention is to allocate money to regions from this source on a population basis, which would give the Auckland region about 35 per cent or about $72 million.