There is more stuff going on on the roads you travel than you would have ever thought to ask; anyhow, there was more than I expected to find. In no particular order, here are some of the cooler sites I found when trying to make sense of the road system – the craziest infrastructure. Asphalt bubbles up from the ground naturally, in lakes. Ninety-three percent of American roads are paved with asphalt, and in asphalt paving, 95 percent of the mix is plain old gravel. More stuff like this here: http://www.hotmix.org/index.php?option=com_content&task=view&id=21&Itemid=41 Are our bridges falling down? Well, of course they are. The Federal Highway Administration posts the National Bridge Inventory, but it's an enormous database. To check your local bridges you're better off going to this interactive database: http://nationalbridges.com/. Just the same, if you want to learn more about how your roads are built and maintained, a good starting place is the infrastructure site that the FHWA manages: http://www.fhwa.dot.gov/infrastructure/infrafact.cfm. An amazingly cool thing the FHWA makes available is the MUTCD – the Manual of Uniform Traffic Control Devices. Rules for how to, say, sign a detour for two overlapping routes? [http://mutcd.fhwa.dot.gov/htm/2009/images/fig6h_09_sm.gif]? It's all – and I mean all – there for you at http://mutcd.fhwa.dot.gov/kno_2009.htm. Ever wonder what rules they're following when they choose Interstate exits and signs? Wonder no more: http://web.archive.org/web/20080211200222/http://users.adelphia.net/~pwolf/controlcities.html Good information about the vast amount of work we need to do on our roads in the aptly titled "Rough Roads Ahead," put out by AASHTO, the American Association of State Highway and Transportation Officials: http://roughroads.transportation.org/RoughRoads_FullReport.pdf In fact the AASHTO website is a good place to start for all kinds of general information on how we get where we're going: http://www.transportation.org/ The highway interchange – you know, the cloverleaf, the diamond, the SPUI – rarely gets its due as a cultural artifact. This website -- http://www.kurumi.com/roads/interchanges/ -- not only provides a sort of Peterson's Guide to the Interchanges of North America (want to know what a SPUI is? You'll find it there), it chronicles the appearance of highway interchanges in movies ("The Blues Brothers") and computer games (Sim City).