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VIP guests nibbled on sandwiches at the official opening of a new toll road north of Auckland yesterday - while hundreds of frustrated drivers sat in queues north of Orewa on State Highway One.

The $365 million Northern Gateway toll road is designed to cure the Orewa bottleneck, but was not opened to the public in time for the Auckland Anniversary Weekend exodus.

Instead, it remained closed while Transport Minister Steven Joyce, Rodney Mayor Penny Webster and other invited guests attended a mid-morning ribbon-cutting ceremony under the toll gantries. While guests were treated to light refreshments and a leisurely coach tour of the new road, traffic on SH1 was so heavily congested that by 11.30am police were advising drivers to consider a longer, alternative route.

New Zealand Transport Agency spokesman Ewart Barnsley defended the timing, saying the road was opened as soon as possible. Finishing touches such as safety checks and signs were still being made yesterday.

"We were working as quickly as we could to get it open, and it's opening two months ahead of schedule."

Earlier, Joyce stood by the agency's decision to open the new road in the middle of a busy holiday weekend, saying it would offer much-needed relief for homeward-bound motorists.

The new highway offers a sweeping, bush-lined 7.5km short-cut from Orewa to Puhoi. State-of-the-art engineering includes a pair of tunnels and three viaducts.

The new road opened early today and will be free of charge until Monday midnight. After that, a one-way trip will cost nothing for a motorcycle, $2 for a car and $4 for a truck.

Drivers can pay at cash kiosks at either end, by credit card on freephone 0800-402020 within three days, or via pre-paid accounts.