Hard problems are not necessarily solved by complicated tools. Sometimes solutions can be found from simplicity.
But these days, scientists and engineers are looking at mother nature for examples: http://www.popsci.com/technology/article/2011-08/13-year-old...
While there's rebuttal about why the solution above won't work: http://www.smartplanet.com/blog/thinking-tech/why-13-year-ol...
It's still gives us some perspective and thought of how nature restructures things in a certain way. We could possibly build on that.
Ant traffic is handled by several simple rules. Maybe there's something we can learn from them too? We're already considering the removal of traffic lights - initially thought to help manage traffic flow. Do we necessarily need to manage them? Maybe.. maybe not.