LPR is unlike GPS devices, RFID, or other technologies that may be used to track. LPR is not ubiquitous, and only captures point in time information. And the point in time information is on a vehicle, not an individual. Individual drivers are already protected under the Federal Driver's Privacy Protection Act (DPPA). In the event that a vehicle becomes of interest in an investigation, it is still up to the officer to place a driver with the vehicle at the time of the crime. LPR data is an investigative lead only.
In a recent meeting, a well known user of LPR took exception to the use of the word "tracking." She highlighted that, with permission, she ran the Mayor's plate in the LPR system and had seven sightings over the last year. Paraphrasing, she said, "That's seven seconds in the course of a year. Over 31 million seconds in a year. We knew where the Mayor's vehicle was for 0.00002% of the year, and we don't know if the Mayor was driving. Is that tracking?"