Hundreds of tourists attempting to enter Queenstown from the Remarkables ski area and hundreds of residents trying to get home to Kelvin Heights and other southern estates were gridlocked about 5pm when a power outage, believed to be have been triggered by nearby construction, caused the signals to suddenly go out of sequence.
The equipment which runs the signal phasing was upgraded in April, to allow a quicker flow of traffic over the bridge.
A team of Opus consultants on site to survey the effectiveness of the changes were among the drivers stuck in the traffic jam and were among many drivers to raise the alarm.
Queenstown police received calls from ''irate motorists'', Senior Constable Chris Blackford said.
A temporary repair was made on Thursday night, but congestion still took a long time to clear, New Zealand Transport Agency Central Otago area manager John Jarvis told the Otago Daily Times yesterday.
''It was a one-off situation,'' he said.
Work begins today to replace damaged electrical components, check software and fully restore the signals to the corrected phase times. A manual stop-go traffic management system was used over the weekend.
About 450 vehicles cross the bridge an hour, rising to about 580 an hour between 5pm and 6pm.
The transport agency in March proposed, ''in time'', to realign State Highway 6 to cross the Kawarau River on a new $18 million two-lane bridge.
A new bridge is not expected until after 2015.
