I don't know why they don't change it to RUC for every vehicle; get rid of the variable of fuel usage.
If you drive an older car that gets 10l/100km, you pay at least twice the road tax as someone that drives a modern hybrid that is in the 4-6l/100km range. So the road tax is favoring those that can already afford to buy a modern efficient car.
That was a campaign promise, and is part of the coalition agreement between National and Act, as far as I know.
There have been discussions around an E RUC system, which I hope comes through. The existing systems are aimed at companies rather than individuals, and buying RUCs is a pain in the ass.
It isn't too bad; I buy online and the ticket comes in the mail. It could be better (much better) but it isn't too bad.
I see the big issue being the minimum weight of 3.5T; if I'm driving a 1200kg carolla, it is a bit rich saying I'm doing the same damage as a ute / light truck / big van.
If/when the eRUC system gets implemented, there are going to have to be a lot more categories.
They will absolutely need to introduce lower levels, I suspect
motorcycles may just pay a flat rate at registration time. Buying online isn't too bad, but you do need to check your odometer against your RUCs every so often, and it's easy to end up behind. It's also annoying to have to pay in a big lump every so often rather than as you go with fuel.
I'd love to have an automated system that just charges you every thousand KMs with no action required by me.