I could easily be wrong on this, but I've always believed that the greater part of our petrol tax is absorbed into the 'General Fund' - from which a small part is applied to roads; a probably-equal amount is siphoned off to pay for railways, ferries, etc; and the greater amount goes to general Government wonderfullness.
On the back of an envelope...
If 2 M kiwis drive 12 K and burn 8 L per 100K, that's 2 B L per year.
It looks like the actual retail cost of petrol is about 0.70-90 $NZ/L.
So that should give the NZ Government 4 billion dollars a year - from private road users.
Plus $$$ from commercial road users, which I've heard is about equal.
So, my best guess is 8 B $NZ income.
On top of that we have registrations - which may, hopefully, raise more $$ than the bureaucracy set up to collect them.
Also tolls - ditto.
Also fines and infringements - which may go some way to paying for enforcement.
Looking at the formal NZG 2021 Budget document, it looks like 2 B $ for all Transport expenditure - but the whole document is mired in 'Wellbeing Strategy' and is structured so that only Woke activity seems to be allocated any money - anything as disgusting as roads is as deeply buried as possible. Above my pay grade...
Anyone found any believable numbers on the subject of income from & expenditure on behalf of the Kiwi motorist ?