Cool. I did a traffic visualization from my apartment on Haight Street on New Years Eve and the first week of January this year. I just had a webcam with some software to detect movement in the middle of the intersection.

http://tlrobinson.net/projects/haightcam/traffic.png

(My R skills aren't great, sorry it's not pretty. The camera also got blocked for awhile around day 5 so it's not exactly scientific)

That first cycle starts mid day on New Years Eve. You can see a big drop in traffic leading up to midnight, then a big increase soon after. Not surprising, but it's always a little gratifying to confirm a hypothesis.