Construction of a new rail link between the Port of Auckland and the Wiri Inland Port is complete, with the first train due to arrive at Wiri at this week.

Ports of Auckland managing director Jens Madsen said completion of the rail exchange was a major step forward for the port company and for the Auckland region.

"New Zealand needs top quality infrastructure and a flexible mix of sea, road and rail transport options, if our economy is to grow," said Madsen.

"Adding a rail option to the Wiri Inland Port brings Auckland and the upper North Island is definitely a step in the right direction."

"This is about bringing the seaport right to the doorstep of businesses in South Auckland. Exporters and importers will be able to drop off and pick up containers without having to negotiate the Auckland motorways."

There are also big potential benefits for the community through reduced road congestion, with the rail link forecast to eventually save up to 2.5 million truck kilometres per year ?C the equivalent of 100,000 central city truck trips.

Madsen said carbon emission modelling by Ports of Auckland had shown big potential savings for businesses close to the Wiri Inland Port.

"A lot of our current customers are based within eight kilometres of the inland port. By using the rail link to the seaport, this group will be able to reduce the carbon emissions of transporting their containers by up to 25 percent," he said.