The Transport Ministry has again floated the banning of importing petrol and diesel cars by 2035 so New Zealand does not become a dumping ground for old cars.

It's part of a high-level look at how New Zealand's transport system could reduce its emissions to zero by 2050. Transport currently makes up about half of our emissions.

The government says it wants a "national conversation" about the changes needed to reduce transport sector greenhouse gas emissions.

Minister of Transport Michael Wood has released Hīkina te Kohupara - Kia mauri ora ai te iwi - Transport Emissions: Pathways to Net Zero by 2050, a Ministry of Transport report outlining potential policies and pathways to a net zero emission transport sector.

"Reducing emissions across the transport sector is an enormous undertaking, but it is achievable and will help support our economic recovery," Wood says.

"The transport sector currently produces 47 per cent of New Zealand's CO2 emissions and between 1990 and 2018, domestic transport emissions increased by 90 per cent.

"We've already taken steps to reduce emissions but Hīkina te Kohupara shows we have to go much further.

"The pathways laid out in the report show it's possible to meet our emission reduction targets, but big changes will be needed in the coming decades. There will be some hard choices to make, but it's obvious we can't continue with business as usual."

But the ideas in the report, which also includes options such as scrapping existing highway projects and banning fuel-burning cars and vans by 2050, are not policy.

The government wants a "national conversation" about the changes needed.

"We want to hear from the public over the coming weeks, and we will then consider the suggestions in Hīkina te Kohupara. Our Emissions Reduction Plan will be released by the end of the year," Wood says.

Consultation is open for six weeks until 25 June.

• RNZ