How ALPR works

Top 5 Next-Gen Cop Car Gadgets November 2007.
> Here are the five:
> 1. Carbon Motors E7
> 2. Project54 Voice-Command System
> 3. Automatic License Plate Recognition Cameras
> 4. StarChase GPS Launcher
> 5. Rumbler Intersection Clearing System
> Popular Mechanics article

 http://www.popularmechanics.com/cars/news/preview-concept/4231942?page=1

3. Automatic License Plate Recognition Cameras
In any appraisal of high-tech policing, you're bound to brush up against Big Brother-worthy technology. Case in point: Automatic License Plate Recognition (ALPR), which is essentially cameras that run every single plate they see. According to Brian Shockley, vice president of marketing for Tennessee-based PIPS Technology, the leading manufacturer of ALPR, the most common configuration is a three-camera system. All of the cameras have a fixed position and focal length, with two facing forward—one scanning the lane to the right of the car, the other scanning the lane to the left—and a side-mounted camera intended for parking lots. Each camera sends a constant stream of infrared and full-color images back to a processor in the trunk, which searches them against current warrant lists, Amber Alerts and other records that are updated daily. "The officer gets results in near real time," Shockley says, "or about 20 milliseconds."
The cameras work at high speeds, with 180-mph differentials. So whether a car blazes by a stationary police car at 140 mph, or passes in an oncoming lane while both cars are doing 80 mph, the system should pick up the suspect's plates.
But here's where things get creepy: Since each agency determines how long to keep the reams of data collected daily by each ALPR system, investigators could potentially search through thousands of drivers in a given area, during a given period, to help track down a hit-and-run driver. And PIPS sees the technology being installed on nonpatrol vehicles as well, such as street cleaners. Nothing, in fact, is sacred.
Short-Term Impact: PIPS hasn't provided exact numbers, but despite its relatively high price tag—a three-camera system costs around $25,000—ALPR systems are already in use across the United States, including agencies in California, Arizona, Texas and New Jersey.
Read more: Top 5 Next-Gen Cop Car Gadgets - Popular Mechanics