[CalRobert]

I think most roads should be paid for by tolls and taxes reduced accordingly. This is because roads tend to have a huge number of negative externalities.

In some cases the very act of having to pay increases the utility of the road to the user - see congestion charging. This ensures people who gain the most economic benefit from using the road are the ones using this precious resource.

Of course, your point could be applied to any government-provided service where there is a fee. The tram receives public funding but I still have to buy a ticket, after all.