Congestion charges could help ease traffic at peak hours

The Economic Research institute has looked at how to fund upgrades for New Zealand's roads, cycleways and public transport in a carbon-zero future.

It says inner city tolls could be the most efficient way to fund infrastructure - and ease traffic in the country's main centres.

But NZIER principal economist Chris Nixon says it's early days.

He says it's highly dependent on the geography of the city and the cost of implementing the systems.