WANT to buy a bridge, or at least invest in a company that builds one? (No, that bridge is still not for sale.) Skip to next paragraph Enlarge This Image Benjamin Sklar for The New York Times Enlarge This Image Darren Hauck for The New York Times As they search for better returns, more investors are discovering that the road to riches could lie in the vast global infrastructure: an assortment of companies that build or manage highways and tunnels, water and waste systems, parking garages, airports and other properties. These rather obscure investments offer predictable cash flow, largely impervious to economic and market fluctuations Join discussion...