Thousands of motorists spent hours stewing in traffic jams between Auckland's Northern Gateway toll road and Warkworth yesterday.
Traffic started banking up north of Puhoi at about 10.30am, and three hours later was jammed for about 25km from Warkworth back to the Hillcrest Rd bridge over the southern end of the toll road at Orewa.
The worst problems were where lanes merged, whether at the end of passing lanes or at the northbound entry to the Johnstones Hill tunnel at the Puhoi end of the toll road.
It was not until 4pm that the Transport Agency reported a relatively free flow had been restored to the tunnel, which is confined to one northbound lane for safety reasons at the other end, where traffic from the alternative free coastal route through Orewa merges with State Highway 1.
Transport Agency northern highways manager Tommy Parker said State Highway 16 through Helensville remained free-flowing throughout yesterday as an alternative route to Wellsford, and drivers should always consider that option if travelling further north over the holiday period.
The agency regards December 27 as traditionally its second busiest day for traffic over the Christmas-New Year break after January 2 for the main road north from Auckland, with about 50 per cent more vehicles than the daily average, but Mr Parker said yesterday was even worse than usual.
"It was particularly bad this year - we have seen some quite large delays made worse by a lot of vehicles towing boats and caravans," he said.
"We had expected the traffic would spread across a number of days, but people decided to travel on the same day."
Mr Parker said traffic was unexpectedly light on Boxing Day, and he was at a loss to know why.
"Presumably people were all at the races or the sales."
But after yesterday's chaos, he was confident the traffic would also be "significantly lighter" today.
Despite extra difficulties observed by Herald staff where traffic ground to a standstill in attempted mergers at the end of passing lanes, Mr Parker said the agency was not considering temporarily closing the lanes to simplify flows.
He said that had not been done for years.
The agency had discontinued the practice because it believed some drivers became confused and erratic when confronted by cones blocking the lanes.
As well, the agency had no evidence that blocking the lanes improved flow.
Neither did he believe motorists had been short-changed by paying $2 to use the toll road, only to be forced to a slow grind little more than 2km along it, during the worst of yesterday's congestion.
He said electronic signs south of the road warned drivers of queues ahead, giving them options of going to SH16 from the Silverdale interchange or using the Hibiscus Coast highway, which was also relatively free-flowing until it merged with SH1 near Puhoi.
The agency reported that other routes out of Auckland - including the Kopu Bridge at the gateway to Coromandel Peninsula - were relatively free of congestion yesterday.
But a police armed offenders' squad callout caused traffic jams around Matatoki on the Thames-Paeroa road southeast of the Kopu Bridge.