Holidaymakers returning home from Central Otago were stuck in a massive queue between Beaumont and Raes Junction this afternoon.
Witnesses said the lights at the Beaumont Bridge were not operating properly, causing traffic to back up about 6km from the bridge all the way to nearly Raes Junction.
A Waka Kotahi NZ Transport Agency spokeswoman said the problem was caused by "a traffic light sequencing fault" which took about an hour to resolve from the time the agency was notified.
"A traffic manager is on site now and will ensure no further hold-ups for people in either direction."
Monday, Labour Day, is a public holiday.