Auckland Harbour Bridge - Traffic Management

Traffic Management

A "tidal flow" system is in place, where the traffic direction of the two centre lanes is changed to provide an additional lane for peak period traffic. During the morning peak five of the eight lanes are for southbound traffic. This is reversed in the afternoon, when five lanes are allocated to northbound traffic. At other times the lanes are split evenly, but peak traffic has become proportionately less - in 1991 there was often a higher than 3:1 difference in directional traffic, in 2006 this had dropped to around 1.6:1. The bridge has an estimated capacity of 180,000 vehicles per day, and in 2006 had an average volume of 168,754 vehicles per day (up from 122,000 in 1991).

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. Two specially designed barrier machines moved the barrier by one lane four times a day, at a speed of 6 km/h. It took 40 minutes to move the barrier, which was the first of its kind in the world.

In March 2009 the barrier transfer machines, which had lasted four times their original design life of five years, and the original barrier were replaced. The new machines are capable of moving the barrier in half the time the old machines did. The concrete barrier blocks and the metal expansion blocks have been reduced in width by 200 mm, giving more width in the lanes either side of the barrier.

As part of the Victoria Park Tunnel project, the moveable barrier has been extended southwards to the Fanshawe Street onramp.