Transport Minister Phil Twyford said the report showed the benefits of investing in rail.

New Zealand's rail network has save the country $1.5 billion by reducing congestion wait times, accidents and emissions, a report has found.

The total cost avoided by having passengers off the roads and on rail was $1.19b alone, according to consultancy firm EY.

Their report was produced in 2016, commissioned by the New Zealand Transport Agency (NZTA) but the former government never released it.

STUFF A year-old study, just released by the Government, shows $1.5b in savings of congestion and safety incidents, by having a rail network.

New Transport Minister Phil Twyford said the study supported further investment in rail, and reinforced the Government’s plans to do so.

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EY found the net benefits provided by passenger rail amounted to $1.2b in savings from reduced congestion, $8.2m in safety benefits and $3m in reduced emissions.

For freight, there was an estimated total net benefit of $354m.

"The implications of these findings for passenger rail is that the support it receives from subsidies (central and local government) is highly likely to be acceptable because passenger rail is calculated to add significant value by reducing congestion on Auckland and Wellington's arterial roads," the report said.

"The implications of these finding for freight rail is that the Government funding it receives is likely to be acceptable as the total benefits (both quantitative and qualitative) could be greater than the Government support it receives."

However, the study had a number of limitations across all measures, said EY, and a more analysis was needed to confirm freight rail's benefits outweighed the subsidies afforded it by Government.

The study also broke down the time delay costs for the two major cities; Auckland and Wellington.

In the capital, it found that even with its passenger rail system, 19.8m hours worth of congestion came in at a cost of around $303m in time delay. In Auckland, the traffic situation was more complex.

The net time delay cost was about $882m, and the report's writers said that represented an 57m extra vehicle hours on Auckland roads.

Twyford said rail was a "great way to travel and move cargo".

"It takes both passengers and freight off the roads, improving the travel experience of road users and reducing their costs."

The Government would "restore balance" to transport funding and boost investment in rail infrastructure both for passengers and freight.

"This will include significant investment in regional rail via the Regional Development Fund, as set out in the Labour-New Zealand First coalition agreement.

"The establishment of a light rail network in Auckland will significantly increase the $1.3b a year of benefits that road users, including freight companies, experience from reduced congestion," Twyford said.