Fred Foldvary claims that "A pure free market would not experience 
periodic traffic jams", but his argument is actually about a pure 
free market in which use of roads is commoditised (whether by 
government or otherwise).

In the (usual) case where use of roads is "free" (at the point of 
use, like the UK's NHS), it is nonetheless the case that this is a 
free market (modulo traffic regulations, etc.) where users pay extra 
to use the road during busy periods -- the difference is that they 
pay in kind (i.e. in time).

As he rightly says, the outcomes of a spontaneous order are not 
necessarily pleasant ...

Julian Wells