Other ideas for improving spending include coordinating highway, transit and railroad administrations so that they actually link up in a rational fashion — right now, the United States is the only industrialized country that doesn’t do this. A 2005 GAO report, for instance, found that “Most major U.S. airports have direct connections to local transit systems rather than to nationwide rail or bus systems.”
I mean, I don't have any problem running the inter-city rail system through the airports, but I can't see why it would be a priority worth spending much money on. If there's a rail line nearby when you're thinking of building an airport, or vice versa, sure spend a little extra to add a link, but I don't think it's a priority.