On Tuesday, one of the largest LPR manufacturers, ELSAG, announced a major upgrade to "allow investigators to search by color, seven body types, 34 makes, and nine visual descriptors in addition to the standard plate number, location, and time."

Such a vast expansion of the tech now means that evading such scans will be even more difficult.

For years, Ars has been reporting on automated license plate readers (ALPRs, or simply LPRs)—a specialized camera often mounted on police cars that can scan at speeds of up to 60 plates per second.

Those scans are compared against what law enforcement usually dubs a "hot list" before alerting the officer to the presence of a potentially wanted or stolen vehicle. All scans are typically kept in a police database for weeks, months, or years on end.

These devices are now in common use by cities big and small across the United States, as well as many countries around the globe, including the United Kingdom. Police at the upcoming royal wedding in London will use LPRs to monitor unauthorized vehicles.

"Using advanced computer vision software, ELSAG ALPR data can now be processed to include the vehicle's make, type—sedan, SUV, hatchback, pickup, minivan, van, box truck—and general color—red, blue, green, white and yellow," ELSAG continued. "The solution actively recognizes the 34 most-common vehicle brands on US roads."

Plus, the company says, the software is now able to visually identity things like a "roof rack, spare tire, bumper sticker, or a ride-sharing company decal."

Many law enforcement agencies believe that using such technology does not require a warrant and is currently allowed under the 1983 Supreme Court case Knotts v. United States, which found that there is no "reasonable expectation of privacy" when traveling on a public road.

That case, which involved one 1970s-era car being followed along a Minnesota highway during a single day by police who used a low-range FM transmitter to track its movements, is far different from the technological reality in which we find ourselves today.