Working with circles seems weird. I would have computed a Voronoi tessellation with Fortune's algorithm (also n log n) and colored the result with OpenGL triang

Working with circles seems weird. I would have computed a Voronoi tessellation with Fortune's algorithm (also n log n) and colored the result with OpenGL triangles. Even better would be to estimate traffic density of the roads based on road type and some measure of centricity/connectedness and also weight the resulting values with that. A small central spot sourrounded by small streets may be calmer than a large peripheral one right next to a high way.