The opportunity cost of freeways

"Opportunity cost" is an economic term to describe the cost of spending money one way instead of another.  Consider the penchant for "across the board cuts" in government spending.  If a family were to do that say with "across the board cuts" in its grocery spending, the kids would suffer.  That is, if Dad cut his beer spending by 25% and the spending on milk by 25%, then the opportunity cost of Dad's beer would be less healthy children.

Every time I drive through the mammoth interchange of I-35 and I-694 in the Twin Cities, I think of all the houses or farms that could be in that space.  I think of all the property tax that has been lost so people ever farther out can get between here and there in a "minimum" amount of time.  Could the lost tax revenue have gone into more public transportation, moving more people with less space?  If public transportation was more widely used, would more people spend less time in traffic when weather conditions make driving difficult?  I'm sure you can think of many more costs associated with complex highways that could be better spent elsewhere.