From a reader who, by his credentials alone (can’t divulge ‘em), is qualified to be my Transportation Guy:
Whatever the other benefits of road spending, it doesn’t work as SHORT-TERM economic stimulus because the highway program “spends out” incredibly slowly. CBO testified this week that even if you sign a bill into law tomorrow, for every billion dollars of new highway money you provide, less than one-fourth of that money can actually be spent (outlays, a.k.a. checks cut by Uncle Sam that can be converted to real money spendable in the real world) in the first year. Most of the money doesn’t spend out until between the second fiscal year and third fiscal year after the funding is first provided, and it takes about eight years, on average, for the funding to be completely spent out. This is because of the time required for metropolitan planning, environmental impact studies, land acquisition, bidding, etc. And CBO pointed out that because highway funding takes so long to spend out, by the time cash makes it into the real world, the recession may be over, and the countercyclical value of the extra money is gone and it may become inflationary stimulus. Though more infrastructure spending is certainly needed, it can’t be viewed as a short-term stimulus and needs to be part of an overall long-term (50-year or so) capital plan.