Transmission Gully would likely take longer to clear than the coastal highway after a major earthquake, the Minister of Transport, Stephen Joyce, admitted in Parliament today.

Mr Joyce who was answering questions from Green Party MP Sue Kedgley confirmed that it would likely take three weeks to clear Transmission Gully in the event of an earthquake.

"This admission undermines the main justification for building Transmission Gully-namely that it would provide an alternative out of Wellington in the event of an earthquake," Ms Kedgley said.  "It is madness to build a new motorway on an active earthquake fault."

A Ministry of Transport report also notes that the steepest section of Transmission Gully is a 3.3 kilometre climb that is roughly twice as long, and half again as steep as the Ngauranga Gorge, and as a result truck operators may prefer the coastal highway .

Ms Kedgley said the report obtained under the Official Information Act confirmed that roading engineers proposed escape routes and ‘arrestor beds' for out-of control vehicles travelling on the extremely steep section of the proposed motorway.

Meanwhile Transmission Gully was expected to increase commuter traffic, reduce rail use and that there was ‘a substantial potential for increased congestion' around Porirua.

"Why on earth would the Government build a motorway that is predicted to increase congestion and reduce public transport?" Ms Kedgley asked. 

"Transmission Gully is a lemon. Most roads require a positive cost benefit ratio of 4 or 5 to be built, and it would be absurd to build a new motorway on an active earthquake fault that only has a cost benefit of only 0.36 to 0.50."