Computer Generation of Road Networks

For the past couple of days, I've been thinking of how to get a computer to automatically generate a city road network. I really have no idea what the best way to approach this is.

Doing a quick search through the Internet, there are computer techniques for automatically generating terrain, for simulating the growth and sprawl of cities, for simulating the growth of small neighbourhoods, and for simulating traffic on a road network, but only a few simulations for generating accurate road networks themselves. In fact, the simulations that do exist seem to focus on simulating lot use with the expectation that the road network just sort of "falls out."

I think the difficulty is that there isn't that much scientific use for simulating the development of road networks, so a lot of research hasn't gone into that area. Of course, the people who do research on urban sprawl really should do more research into road networks too because urban sprawl tends to be dependent on the location of existing highways etc. Anyways, the problem is also hard because road networks tend to be highly planned and need to take a lot of factors such as geography, cost, etc. into account during their evolution, so it's hard to get a computer to randomly generate this type of data.

Still, I wonder what it takes to build a road network generator. I imagine that an urban growth simulation model might actually be the wrong approach because it'll end up being too complex. I think a top-down approach that lays out some highways, throws down a coast-hugging road network near water, builds a grid patterned downtown, and a squiggly suburb area might actually be the easiest approach. Hmm.