Here’s an article about proposals to increase the level of permitted density in Reston as Metro extends heavy rail access out to the area. As you know, I’m generally pro-density, so of course I support this.
But more broadly I would say that state and federal transportation funders should make local approval of increased density a condition of appropriating money for new transportation infrastructure. You wouldn’t build a road network in an empty area unless you were planning on putting some development there. And by the same token, the thing that makes rail transportation useful is that it makes high densities logistically feasible. Of course in any given location there will be a market limit to how much density can be supported, but if you build the infrastructure without increasing the regulatory limit you’re basically just transferring wealth to owners of existing structures.