In the 1980s, tidal flow was introduced on the Auckland Harbour Bridge to assist with peak flows on the Northern Motorway between the North Shore and central Auckland. The two central lanes were made reversible to allow a 5+3 split favouring the peak direction (southbound in the morning, northbound in the evening) during peak hours, and 4+4 off-peak. The lanes were controlled by overhead signals, which some motorists on the Motorway ignored and were killed when they collided head-on with oncoming traffic - between 1 January 1989 and 27 November 1989, some five people died as a result of collisions involving the so-called "suicide lanes". In 1990, a moveable barrier was installed to separate the traffic flows.