The federal highway system--the "Interstates," like I 35W--has a total length of about 50,000 miles, and though that is only 1 percent of the total highway mileage in the United States, it carries almost a quarter of the nation's total road traffic, amounting to some trillion persons a year, and half its truck traffic.From Richard Posner's analysis of the Minneapolis bridge collapse and the infrastructure "crisis" (quotation marks his, emphasis mine).
Truly even libertarians and economists might have to acknowledge the vast efficiency gains from certain public infrastructure investment. At least we must say there is some unappreciated economy of scale going on here.
UPDATE [8/31 1:43pm EST]: Some related reading
--In "The New Privatization," Steven Malanga overviews the turning over of major freeways in
Indiana, Chicago, and elsewhere to the private sector.
-- Back in 1992, Anthony Downs (who had previously made his name by writing one of the most cited books on the economics of voting and democracy several decades prior) wrote the bible of the economics of traffic.
--Google Maps introduced real time traffic info back in February. Where have I been?