Harbour bridge misses out on upgrade

Very heavy trucks may be forbidden to use the Harbour Bridge. Photo / Herald on Sunday

Auckland Harbour Bridge has been left off a list of highway upgrades needed to cope with heavier trucks, despite a report last year warning of a need for further strengthening.

The Transport Agency says consultants qualified to conduct a specialised engineering assessment of the bridge have been unavailable, although it expects the work to be done before a rule change allowing 53-tonne trucks on key routes is introduced next year.

Even so, the Auckland landmark's absence from an assessment of 306 bridges serving 37 per cent of the highway network has been cited by opponents of the rule change as more evidence of insufficient analysis of the costs of increasing the existing 44-tonne limit.

The agency estimates it would cost $85.36 million to upgrade 163 of those bridges against what Transport Minister Steven Joyce says could amount to annual productivity increases of $250 million to $500 million from the rule change.

Further studies are recommended for the other 143.

But the Auckland-based Campaign for Better Transport, as well as Local Government New Zealand, is asking why the impact on other parts of the network and local roads has not been included on the cost side of the balance sheet.

"Normally when you own a business you analyse the costs and estimated profits, but they've looked at the benefits and not analysed the costs," said campaign spokesman Jon Reeves.

The Ministry of Transport has meanwhile refused to publish a report of road trials on which Mr Joyce based his productivity estimate, as it says the document contains commercially sensitive data gained from freight companies, although it is still considering an Official Information Act request by the Herald.

Although the Transport Agency agreed late last week to issue its bridges report to the campaigners, they are upset it waited until 24 hours before a deadline for submissions on the rule change.

Agency spokesman Andy Knackstedt said that although more than 130 submissions were received by Friday's deadline, anyone wishing to follow up the report could seek an extension.

Noting that the Auckland bridge had not yet been considered for heavier trucks, the report says $45 million of strengthening being applied to its clip-ons is not intended to allow these to carry extra loads under the rule change.

But the report expects that the original truss bridge will be able to carry heavier trucks, even though Mr Knackstedt acknowledged it as "a very complicated structure" requiring a highly specialised engineering assessment to be carried out towards the end of the year.

An earlier report to the agency's board revealed that restricting trucks to the middle lanes was already accelerating damage to the main structure.

Mr Knackstedt acknowledged that 53-tonne trucks might end up being kept off the bridge, and being restricted to Auckland's upper harbour route.

The later report also notes a likelihood of "longer-term fatigue issues" yet to be considered from heavier loads on steel bridges elsewhere, but he said these made up only about 15 per cent of highway crossings.

Asked why the report dealt only with bridges, and not general road surfaces likely to receive extra damage from heavier trucks, Ministry of Transport spokeswoman Lesley Reidy said councils had been asked to outline their concerns and possible solutions in submissions.

The rule change would be only for specific routes, to be approved by road controlling authorities as capable of carrying heavier loads.

* Trucking on

Existing maximum truck weight: 44 tonnes.

Maximum length: 20m.

Proposed new maximum weight: 53 tonnes if permitted by road controlling authorities on routes yet to be specified, or more (no limit specified) if approved by the Transport Agency in consultation with other road authorities.

Proposed new maximum length: 22m.