Tracking people through their vehicles?

They also track speed through loop sensors cut in the lanes at regular intervals, which are simple metal detectors and anonymous. I'm not sure which dept. uses which system though. I believe the yagi antennas you see are simple microwave motion sensors, not fastrak readers (although technically they could be used that way). For instance, the ones used at the dmv weigh stations are aimed high to alert them of 18 wheelers dodging the scales.
On a related subject, but no less sinister - Has anyone read about this new big brother parking scheme for SF?
Of course it always sounds good when they list the benefits for the driver. But I seriously doubt it will help anyone park more efficiently and it could actually make it worse. In my opinion, by giving people gps style alerts, they're more likely to just double park while they wait and then zoom over when a space frees up. How does that help the traffic flow? I can only imagine the fights that will break up when 5 cars show up at the same time contending for the same space. Guess I better start packing a taser! (joke)
But seriously, it's obviously a tactic for the city to milk max revenue from people who park legitimately in spaces. No plans for punishing the double parkers of course, but maybe that will change with the growing budget deficit. I've already heard that the SFPD is cracking down on sidewalk parking in North Beach, so maybe this is all part of a larger city 'revenue enhancing' effort.