If they are paid with tax dollars then they most certainly are... unless they happen to be closed for construction or events and thus closed to all traffic... if they are roads that are constructed by bonds backed by toll revenue, then you are correct in stating that they are not free to use at all times.
Again, a regressive tax is NOT 'market norm'.
All I'm saying is that you have to pay to use certain roads at certain times and that this is a reasonable way for the government to alleviate congestion and is preferable to alternatives in that it brings market mechanisms in to determine who uses those certain roads and those certain times as opposed to other government means of doing easing congestion (i.e. quotas).