I was wondering if anyone has numbers showing the ratio of traffic volume on arterial streets to population density for urban core, city limits, and suburbs? I've recently taken to notice this while living in Chicago and going to school in Rural Minnesota, and expanded the idea when i started spending more time in the south suburbs of Chicago.

It seems that there are as many cars at Madison Ave and State Street down town, 63rd St. and Stony on the South Side, Western Avenue and 95th on the far south side, and 143rd at LaGrange Ave in the distant suburbs (I assume even farther out the arterial streets have the same traffice. The thing is, these places have drastically different population densities. I've never done real research, i was wondering if anyone had real numbers