Auckland Council members have agreed to a detailed study of revenue-gathering ideas such as a regional fuel tax and road pricing.
The assessment aims to find ways of plugging a $15 billion gap in the funding of transport projects in coming decades.
Cr Cathy Casey failed to strike out road tolls from the list, but succeeded in arguing that unions should be added to a consultation group.
While most of the year-long research will go into three options including carpark charges, a longer list of ideas such as visitor and airport taxes, will also be considered.
Public consultation will be part of the process and final recommendations are expected in a year.