Prior to the construction of the bridge, North Shore was a mostly rural area of barely 50,000 people, with few jobs and a growth rate half that of Auckland south. The bridge was originally built with four lanes for traffic, however, the rapid expansion of suburbs on the North Shore and increasing traffic levels, it was soon necessary to increase capacity. By 1965 the annual use was about three times the original forecast. Ten years after opening, two-lane box girder clip-on sections were added to each side, doubling the number of lanes to eight. These are of orthotropic box structure and cantilevered off the original piers. Currently about 170,000 vehicles cross the bridge each day (as of 2019).

The bridge supports several utility services, including water and gas pipelines and fibre-optic telecommunications cables. Using cable supports beneath the bridge three 220,000-volt cables link the Auckland CBD substation to the North Shore substation.