Let's face it: if you consider the cost of materials and equipment, it would be less of a drain on the economy to simply give the people money to stay home rather than build more roads and bridges to nowhere.
Add in the congestion created due to the road construction on an otherwise functional roadway, and you have lost productivity and increased fuel costs on top of it all.
Investing in new High-Tech industries, on the other hand...
-Architects get to design stuff
-CPAs and accountants get to spend money
-Materials engineers get to work
-Construction crews get to work
-IT jockeys get to set up communications systems
-Janitors get to pick up "la basura."
-There's ALWAYS something for the ubiquitous "middle management" to do...
(and I'm sure other groups get covered there, too)
I say we gorge NASA nice and fat, and build a rival public/private agency with the intent to "push" it completely private by 2030, out in New Mexico or California.
See who gets to the moon first, and turns a buck off of it. And watch all that resultant technology make its way back into the marketplace.