Call for concrete highway as quake escape

Concrete should be used to construct the Transmission Gully highway to ensure there is an escape route out of Wellington if a massive earthquake strikes, Porirua City Council says.

But roading experts disagree, saying asphalt and chip seal are easier to repair in the aftermath of a quake.

"I've spoken to the people repairing the roads down in Christchurch and their view is if the roads were concrete they would have a whole lot more problems," Roading New Zealand chief executive Chris Olsen said.

Cracks and holes in bitumen roads can be filled in quickly, but concrete roads need to be rebuilt from scratch as the slabs crack, tilt and break, he said.

The council is putting pressure on the Government to investigate concrete as an option for the entire Wellington Airport-to-Levin road of national significance, estimated to cost $2.4 billion, because of its ability to withstand strong quakes and the increasing price of bitumen.

"I think the whole stretch needs to be guaranteed and the original plan needs to be stuck to; it is an alternative accessway but an economic stimulus as well," Porirua Mayor Nick Leggett said.

The council is asking the New Zealand Transport Agency to consider concrete during the design phase between 2012 and 2014.

NZTA's Wellington highways and network operations manager, Mark Owen, said concrete would be considered.

"We will be carrying out extensive work with our suppliers to ensure that the most appropriate roading materials are selected for the Transmission Gully project, in terms of its durability, function, environment and cost."

Reinforced concrete roads were built in seismic areas, including the west coast of America and Japan, Cement & Concrete Association of New Zealand civil engineer Alan Kirby said.

"How much better concrete is than asphalt or chip seal in a seismic area is really a bit debatable."

However, reinforced concrete roads were more durable than bitumen as they didn't split or crack as easily during a quake, Mr Kirby said.

Concrete was more expensive up front, but less expensive over 40 years because of less need for maintenance.

Mr Leggett earlier called for the Government to "ring-fence" funding for the 27-kilometre Transmission Gully link between Linden and McKays Crossing, instead of delaying or diverting funds to the Christchurch rebuild.

Transport Minister Steven Joyce confirmed last week there may be "timing changes" to one or two major projects within the National Land Transport Fund, but it was premature to say what projects, if any, would be affected.

"I would stress that the Wellington northern corridor is a series of projects taking place over a period in excess of 10 years and any timing changes would be minor."

The Dominion Post