VIRGINIA POSTREL ON INFRASTRUCTURE: Too Many Public Works Built On Rosy Scenarios. “Cost overruns in the order of 50 percent in real terms are common for major infrastructure, and overruns above 100 percent are not uncommon. . . . Promoters of rail and toll-road projects also tend to substantially overstate future use, making those projects look more appealing to whoever is footing the bill. Rail projects attract only about half the expected passengers, on average, while in new research still in progress, Flyvbjerg finds that toll roads (including road bridges and tunnels) fall 20 percent short. (Non-toll roads also miss their traffic projections, but their errors go in both directions.)”