The researchers developed a simple mathematical model that can recreate the characteristic leaf-like patterns that develop, growing a road network from scratch as it would in reality.
The main influence on the simulated network as it grows is the need to efficiently connect new areas to the existing road network – a process they call "local optimisation". They say the road patterns in cities evolve thanks to similar local efforts, as people try to connect houses, businesses and other infrastructures to existing roads.
This is important for transit. The reason being that roads have evolved over hundreds of years often one street at a time. But we always get hammered when one transit line doesn't cure all of the region's ills. The reason being that we're providing core arterial service and depend on the smaller connections to be made by foot, bike, and car. In cities such as New York where the transit system starts to mimic the road network do we see how transit can help everyone with affordability, mobility, and energy independence. I wish folks would realize you have to start small, and grow to a network.