Traffic in several of Auckland's suburbs is so bad some companies are refusing to deliver there, says Infrastructure New Zealand.

A report from the New Zealand Institute of Economic Research yesterday showed traffic congestion was costing the local economy up to $1.9 billion a year, but Infrastructure New Zealand chief executive Stephen Selwood said some areas were bearing the brunt of the problem.

"It is an issue, we're hearing stories of freight companies not going into Devonport now for example," Selwood said.

"They call it the 'black hole', in other words they send a truck in there and it never seems to come back out again.

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"So they just don't deliver there anymore.

"These are the real life effects."

The report also found firms were having to establish offices around the city to provide goods and services quickly.

Selwood said the estimated $1.9b could be a conservative figure, given it was only calculated based on a five day weekday, and did not include social or business costs on the weekend.

He said the report created a sense of urgency for the country to make some changes.

"We understand the prize, and I think that's really important because in New Zealand we tend to focus on the cost all the time and all the reasons why not," Selwood said.

"But what this does is say, this is the potential prize not just to the Auckland economy but to the New Zealand," he said.

"We can't keep mucking around on this stuff."

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The report, commissioned by a range of business groups including Infrastructure New Zealand, suggests Auckland could increase its productivity by about 20 per cent by unclogging its roads on work days.