I recently inquired about Ann Arbor’s use of automated license plate readers, aka ALPRs. This technology can be useful for things like parking violation enforcement (which Ann Arbor uses it for), but depending on a police department’s use of the technology, it can have worrying privacy implications.

This EFF article should help understand the power of ALPR data as well as some of the potential pitfalls (in particular, EFF found that lower-income and minority communities in Oakland, CA were disproportionately subject to surveillance).

My questions were:

• How many ALPRs does the city have now?
• What are they used for?
• What data is collected by our ALPRs? (Just the plate number? The date & time it was seen? The location where each plate was seen?)
• What data retention policy is in place for that data? (Is it used solely to check for expired tags, or are logs kept for days or weeks to aid in investigations?)
• What policies are in place regarding the use of ALPR data? (Do we have some formal policy that enforces who can access logs, for what reasons?)
• Roughly many ALPR records does the city currently have?

I received a friendly response from Police Chief James Baird which adequately addressed my privacy concerns.

Takeaways

In brief, my takeaways from the response:

• The Ann Arbor Police Department has 3 ALPRs; 2 are currently in use.
• They are used by the Community Standards Unit for parking enforcement.
• A list of vehicles with 4-6 or more outstanding violations is periodically put on a USB key and manually copied into the ALPR computers in cars.
• Data is stored locally on the system in-car, not uploaded anywhere.
• Data retention may be 365 or 90 days; Chief Baird wasn’t sure.
• Chief Baird: “The information is never accessed for any other reason other than an immediate ‘hit’ [detection of a vehicle with outstanding violations] … We have had the devices in service for approximately 10 years now and have never accessed the data for any reason. I have no one on staff who even knows how since it’s not used for investigative purposes.”
• Chief Baird: “I also don’t know if location information is captured.”

The complete response emails are available through A2Docs.

An Ann Arbor Police Department ALPR.