What Do License Plate Reader Cameras Do?

Traffic Monitoring Cameras

License Plate Recognition (ALPR) cameras originated in Europe where it is called Automatic Number Plate Recognition (ANPR). In North America, they are called “license plates” instead of “number plates”.  Mobile ALPR is a vehicle-mounted solution primarily used by law enforcement, asset recovery (stolen vehicles), and parking management.  Fixed ALPR cameras are mounted on traffic poles and used for law enforcement and asset recovery.

Here are the laws in 50 States regulating automatic license plate readers.

ALPR uses optical character recognition on images to read vehicle registration plates. The cameras can be used for closed-circuit televisions, HOV carpool/toll road & red light camera enforcement in certain States.  However, they are only used for red-light enforcement on the side of the road and NOT on top of a traffic light or light pole.  A flash must be used in this case for photos.  If you see an ALPR camera on a traffic light or light pole it is not used for red-light enforcement and will not issue tickets.

They can also be used for electronic toll collection on pay-per-use roads and as a method of cataloging the movements of traffic for example by highways agencies. Automatic number plate recognition can be used to store the images captured by the cameras as well as the text from the license plate, with some configurable to store a photograph of the driver. Systems commonly use infrared lighting to allow the camera to take the picture at any time of the day.

Mobile ALPR is used among US law enforcement agencies at the city, county, state, and federal levels. Over 2/3 of all US police departments use some form of ALPR.  Mobile ALPR is becoming a significant component of municipal predictive policing strategies and intelligence gathering, as well as for recovery of stolen vehicles, identification of wanted felons, and revenue collection from individuals who are delinquent on city or state taxes or fines, or monitoring for "Amber Alerts".

With the widespread implementation of this technology, many U.S. states now issue misdemeanor citations of up to $500 when a license plate is identified as expired or on the incorrect vehicle. Successfully recognized plates may be matched against databases including "wanted person", "protection order", a missing person, gang member, known and suspected terrorist, supervised release, immigration violator, and National Sex Offender lists.

In addition to the real-time processing of license plate numbers, ALPR systems in the US collect (and can indefinitely store) data from each license plate camera. Images, dates, times, and GPS coordinates can be stockpiled and can help place a suspect at a scene, aid in witness identification, pattern recognition, or the tracking of individuals.

 The Department of Homeland Security has proposed a federal database to combine all monitoring systems, which was canceled after privacy complaints.   Private sector ALPR cameras have been used for vehicle repossession and recovery, although the application of ANPR by private companies to collect information from privately owned vehicles or collected from private property (for example, driveways) has become an issue of sensitivity and public debate.

Other ALPR uses include parking enforcement and revenue collection from individuals who are delinquent on city or state taxes or fines.  Cameras have been featured in the reality TV show Parking Wars featured on A&E Network. In the show, tow truck drivers and booting teams use the ALPR to find delinquent vehicles with high amounts of unpaid parking fine