The screenshot is the result of four nights of playing. I'm currently moving all non-hightech and farming industry to other regions to reduce pollution.
Pentium QuadCore 2.4 GHz
4 GB RAM
512 MB videocard
Avenues and busses does the trick for me. I've also tried applying subways but there were no need for that and eventually it was just an extra expenditure so I dropped it. The attaches picture actually depict the most trafficed area in my city. Everything else is bright green.