What can be done to lower construction costs of new infrastructure in the U.S. (international input appreciated)

There’s a lot of talk of modernizing and “greening” infrastructure internationally. The United States lags especially behind the rest of the world in transportation infrastructure, and the costs of new projects are unusually high compared to the rest of the world. Existing infrastructure is woefully inefficient: buildings are energy hogs, railroads are slow, locomotives are heavy, airports are increasingly congested and prone to delays, electric grids are aging, and fuel costs are almost guaranteed to go up in coming years. Meanwhile, the country is stuck with slow, congested, crumbling highways and little means of replacing them with more efficient alternatives. Since the 1950s, transit infrastructure has been abandoned and demolished.

What should be done to lower costs of new projects? What could be learned from other countries that have successfully implemented major infrastructure projects? Are the challenges social or financial or both?