New Zealand plans to charge road user charges for EVs next year AFAIK. This is a per km tax, though don't believe it has a weight consideration
For petrol vehicles we tax the petrol instead. This is because the cost of compliance is much cheaper (for the government and the car owner) if we tax the petrol. We don't do that for desil vehicles because a large about of desil is used by farm equipment and other off road vehicles. It's easier to do road user charges than to have a refund scheme for desil taxes.