https://www.techdirt.com/articles/20150 ... data.shtml
Here's the relevant citation:City officials argue in their response that every metro driver is under investigation
records “relating to or resulting in a criminal investigation” are exempt from disclosure under the Act, in particular “nvestigative materials, notes, correspondence, videos and reports.” 65 P.S. § 67.708(b)(16)(ii). Such individual license plate readings and accompanying information are investigative materials that relate to individual criminal investigations, and, as your request indicates, these investigations may result in vehicle stops, arrests, or other police actions..
In other words, Philadelphia PD has expanded the old criminal non-statute of "Driving while African" (the crime of Walter Scott) to "Driving". If you are driving, you are under "criminal investigation".