Harbour Bridge comes of age
by André Hueber 
The devastating bridge collapse in Minneapolis has many Aucklanders wondering whether the same thing might happen here.
All vehicles heavier than 4.5 tonnes were banned from driving on the Auckland Harbour Bridge clip-ons in May after fractures were found.
Although Transit warned in 2003 that the bridge’s two clip-ons might have to be replaced in less than 20 years, an engineering review six months later concluded that the 1969 extensions would probably last at least until 2050.
Transit chief executive Rick van Barneveld said Transit was not keeping any problems with the bridge from the public.
He said trucks caused “fatigue stress” to the clip-ons, and reducing that would mean the additions would last at least a further 40 years. He believed the main bridge structure was sound.
“Nothing would have happened to the bridge. It was just going to keep costing us more and more in maintenance,” he said.
The banning of trucks was later revised when a less strict bylaw was introduced in July 2007. The new guidelines stipulate that vehicles of 13 tonnes or more have to drive within the bridge’s inner lanes, as opposed to the outer clip-ons.
Nevertheless, discussions are well under way between Transit and local councils regarding a second harbour crossing, with the most likely solution being a tunnel running from St. Mary’s bay to Bayswater.
History
The box truss style Harbour bridge opened in May 1959 and took 1000 people to build. Four construction workers died in the process.
The bridge has undergone major upgrades, extensions and the addition of the Japanese manufactured clippon lanes in 1966; the bridge was originally built with four lanes for traffic.
Owing to the rapid expansion of suburbs on the North Shore and increasing traffic levels it was necessary to increase the capacity of the bridge.
In the late 1980s a number of fatal head-on accidents occurred when vehicles crossed lane markings into the path of oncoming traffic.
In 1990, a movable concrete safety barrier was put in place to separate traffic heading in opposite directions and eliminate head-on accidents.
AJ Hackett operates a Bungy jumping and Bridge climbing business for tourists on the Harbour bridge.