Auckland Harbour Bridge

Auckland Harbour Bridge

Auckland Harbour Bridge is an eight lane road bridge that spans the Waitemata Harbour joining Freemans Bay in Auckland City with Northcote in North Shore City, New Zealand. The bridge spans a total distance of 1.15 km with a main span of 243.8 m and rises 43.27 m above the high tide level.

Prior to construction of the bridge, the quickest way of getting from Auckland City to the North Shore was via one of the regular passenger or vehicular ferries. By road, the only route was through West Auckland, a distance of some 20 kilometres.

Construction

The bridge took four years to build and was opened on May 30, 1959 by the then Prime Minister Sidney Holland. It originally had four lanes of traffic, two in each direction. Four men were killed during construction of the bridge, and their names are recorded on a memorial plaque located underneath the bridge at the Northcote end.

The bridge started out as a toll bridge, with toll booths located at the northern end. The government discontinued tolling on March 30, 1984, and the booths were removed.

The 'Nippon clip-ons'

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. Only ten years later in 1969, two-lane box girder clip on sections were added to each side, doubling the number of lanes from four to eight. These sections were manufactured by Japanese contractors, Ishikawajima-Harima Heavy Industries Ltd, which led to the nickname 'Nippon clip-ons'.

Traffic Management

A "tidal flow" system was implemented whereby the traffic direction of two of the centre lanes is changed in order to provide an additional lane for peak period traffic. Thus during the morning rush, 5 of the 8 lanes are allocated to southbound traffic heading towards Auckland city centre. This situation is reversed in the afternoon when 5 lanes are allocated to northbound traffic. At all other times of the day, the lanes are split evenly.

For many years lane directions were indicated by overhead signals. 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. Specially designed barrier machines move the barrier by one lane four times a day at a speed of 6 km/h. It takes 40 minutes to move the entire barrier.

Traffic congestion issues at peak times have led to the bridge being referred to as "The Car Strangled Spanner" in a parody of the national anthem of the United States of America.

Plans

The clip-on sections have a lifetime of 50 years and will need to be replaced by 2016. Before the clip-on sections are replaced, another harbour crossing will have to be constructed to cope with the ever-increasing volume of traffic that uses the bridge every day. Several solutions have been proposed, including another bridge built alongside the existing bridge or a tunnel under the Waitemata Harbour. Following a detailed scoping study undertaken in 1996, Transit New Zealand has identified its preferred options for a new crossing – either a new bridge structure approximately 500m west of the existing bridge connecting to a tunnel underneath the city suburbs of Ponsonby and Grey Lynn to the North-Western motorway, or a sub-sea harbour tunnel slightly to the east of the existing bridge connecting to the Central Motorway Junction via twin cut and cover tunnels under the western CBD. These options are by no means final, however, as Transit must first obtain resource consents (town planning permission) from the relevant statutory authorities, who may insist on changes.

External links

• The NZ Transit Authority has some historical photos of the bridge.
• More historical bridge pictures on a private homepage.
• Structurae entry
• Satellite picture on Google Maps