I seem to recall there's term for when tax revenues are strongly linked to tax expenditure. Like when you tax road vehicles and use that exact tax to maintain t

I seem to recall there's term for when tax revenues are strongly linked to tax expenditure. Like when you tax road vehicles and use that exact tax to maintain the road network. But I can't recall the term right now. Seeing more of that thing, whatever it's called, seems like a desirable thing. The 'pooled funds' approach to tax/spending does lead to a lot of whacky outcomes.