You'd have to construct a model where you guess the impact of the taxes vs. the impact of potential investment of the same money otherwise. I suspect this is ha

You'd have to construct a model where you guess the impact of the taxes vs. the impact of potential investment of the same money otherwise. I suspect this is harder than it looks because it isn't discussed much ( although it could be that people simply repeat their ideology rather than trying to make it empirical ). Not all bridges and roads are equally valuable. And in some areas, the dominant method of financing new roads is through tolls. I once estimated the number of man-years per day lost to congestion on I75 in Dallas around 1985 . It was quite the figure.