Transmission Gully Motorway

The route of the proposed Transmission Gully Motorway

The Transmission Gully Motorway is a 26 km motorway proposed for Wellington, New Zealand.

Route

It is planned to replace the current State Highway 1 along the coast road between the Kapiti Coast, Pukerua Bay and Porirua. From SH1 at MacKays Crossing, north of Paekakariki, the route rises steeply to the Wainui Saddle and follows Transmission Gully down to Porirua Harbour's Pauatahanui Inlet. It continues south around the outer edge of the Porirua urban area, at one point crossing a 300-metre-long and 90-metre-high bridge, and rejoins SH 1 at the boundary of Porirua and Tawa. The length is 26 km, with a maximum gradient of about 8.3%.

Construction

Proposals have existed for some time, but it was only late in the first decade of the 21st century that serious steps were taken towards construction. The Greater Wellington Regional Council, in preparing its Western Corridor Plan, initially rejected Transmission Gully as unaffordable, preferring to upgrade the existing coastal route, but changed its position after public consultation.

Transport Minister Steven Joyce announced government commitment to the project on 15 December 2009, with a project cost of NZ$1.025 billion. The project has yet to be finally approved, but construction is expected to start in September 2014 and be "substantially completed" in 2020.

Controversy

The Transmission Gully Motorway is controversial, and has been a topic of considerable debate in Wellington politics for some time.

Supporters claim that it will improve access to Wellington City, arguing that the existing coastal route is too congested, is accident-prone, and could be damaged in a serious earthquake. Peter Dunne, MP for Ohariu-Belmont, says that "[i]mproving Wellington City's northern access and egress is a vital key to the future economic performance and prosperity of the whole region, and the Transmission Gully highway is a vital link in that chain".

Opponents of Transmission Gully state that there are better ways to improve access to Wellington. The fact that such a highway would require an extremely steep gradient on its northern-most end and would thus not actually offer any improvement over the existing coastal highway has been recognized by most opponents. The route that the highway must take is along the major fault line of the region, which would make it at least as earthquake prone as the existing coastal highway. Some suggest that the existing coastal route should be upgraded, rather than building a completely new route. This was the original recommendation of the Regional Council, and was put forward as the primary alternative to building Transmission Gully. Public submissions to the Council were in favour of Transmission Gully, and the Council has changed its stance in response. Opponents of upgrading the coastal route say that doing so would cause significant disruption to the communities it passes through, whereas Transmission Gully avoids urban areas. The former Mayor of Porirua, Jenny Brash, has said that an upgrade would generate large numbers of complaints from Porirua residents, and would therefore have difficulty receiving resource consent. Others, such as the Green Party and the lobby group Option 3, believe that the money would be better spent on improving Wellington's public transport, particularly the existing rail line. They argue that the original choice between building Transmission Gully or upgrading the coastal route was a false dichotomy, and that in reality neither option is necessary or desirable.

Cost

Some opponents of the Transmission Gully project believe that its overall cost is too high, and that the region has insufficient funds to spend on it, with a benefit/cost ratio of 0.6. The previous Mayor of Wellington, Kerry Prendergast, has described the project as "unaffordable". It has been suggested that making Transmission Gully a toll road would help resolve this problem, although no decision has yet been taken on the matter, and tolls would only cover a fraction of the funds necessary to build the highway.

Technical and environmental issues

There have been claims that the route of Transmission Gully is problematic — for example, Option 3 describes it as unsuitable due to steep gradients, environmental damage and earthquake hazards. The route passes near Pauatahanui Inlet, an environmentally sensitive wetland area.

See also

• List of motorways and expressways in New Zealand

External links

• Transit New Zealand Tranmission Gully Project
• Wellington Regional Council's adopted Western Corridor Plan (PDF)
• Option 3, a pressure group opposed to the Transmission Gully Motorway