Automated License Plate Readers

By Pam Greenberg | Vol . 23, No. 08 / February 2015

NCSL NewsDid you know?

  • Automated license plate reader (ALPRs) systems combine high-speed cameras and sophisticated software to capture and convert license plate images into data that can be compared with information in other databases.
  • Cameras used in ALPRs may be mobile or stationary and are small enough to be mounted on police cars, road signs or traffic lights, or placed at the sides of roads or on bridges.
  • License plate reader systems can collect a driver’s geographic location, along with the date and time a vehicle was in a particular place.

Automated license plate readers (ALPRs) capture computer-readable images of license plates. These high-tech devices allow law enforcement agencies to compare plate numbers against those of stolen cars or cars driven by people suspected of being involved in criminal or terrorist activities. ALPR systems also are used by the private sector, for example, to repossess vehicles if payments are in default, to monitor parking or to control access to private property, among other purposes. As ALPR use has increased, state lawmakers have begun to address the complex issues they raise about privacy and appropriate uses of the data.

ALPRs are rapidly becoming widely used by law enforcement agencies. A 2012 survey by the Police Executive Research Forum found that 71 percent of police departments responding used the systems, and 85 percent planned to expand their use or purchase new equipment.

Although ALPRs typically are not mentioned in most state public records laws, the data they collect is often considered public, since such laws often are based on the presumption that the information is open to public disclosure unless specifically exempted or otherwise prohibited. The systems, however, have raised concerns that the information collected may be inaccurate, shared without restrictions, retained longer than necessary, and used or abused in ways that could infringe upon citizens’ privacy. Restricting access to ALPR data can protect people from being tracked and alleviate concerns about confidentiality, but it also can limit oversight of government use of the tool.

Concerns About Using Data From ALPRs. The large amount of ALPR data being collected is growing more quickly than are policies and procedures governing their use, say privacy advocates. ALPRs capture and retain the location information and photographs of all vehicles, regardless of whether the driver is a suspect or wanted for a crime. In a review of retention policies of law enforcement agencies in 2012, the American Civil Liberties Union found that many retain data on innocent Americans for long periods of time. Inaccuracies in databases used with ALPRs could lead to false matches of license plates to innocent individuals.

Further, ALPRs can collect detailed location information, such as trips to church, medical facilities, political protests, bars or other locations that could be used to build a profile or permanent record of a person’s movements. This type of surveillance can create a chilling effect on individuals, who may feel pressured to limit their normal activities, say civil libertarians.

Another concern is that workers with access to ALPR data could misuse it for personal reasons or share or sell it without authorization. Also, some private companies reportedly have amassed millions of license plate scans, leading to concerns about the data being shared or sold for questionable purposes.

Benefits of Using Data From ALPRs. ALPRs have been an effective tool for law enforcement agencies, cutting down on the time required for investigations and decreasing costs for agencies struggling with limited budgets. System cameras can scan thousands of plates in a very short time, allowing police to identify stolen vehicles and drivers who have outstanding traffic violations and expired registrations or plates. For example, a 2011 study by the Police Executive Research Forum concluded that ALPRs used by the Mesa, Ariz., Police Department considerably enhanced the productivity of the auto theft unit, resulting in “nearly 3 times as many ‘hits’ for stolen vehicles, and twice as many vehicle recoveries.”

Automated license plate readers are most commonly used for immediately identifying vehicles on a “hot list,” which requires the license plate data to be retained for only a short time. ALPR systems that store data for longer periods, however, can be used to identify patterns of crime and to locate possible suspects or areas of criminal activity. Police can target their investigations to more serious crimes, such as drug trafficking, burglaries or terrorist activities.

Concerns about privacy should be alleviated, ALPR supporters say, because the data collected does not include personal information about drivers and, until the license plate number is matched to other data, it cannot identify an individual. Further, ALPRs collect information that already is publicly available to anyone.

State Action

Ten states have enacted laws restricting or prohibiting use of ALPRs or ALPR data by law enforcement.

Six—Arkansas, Maine, Maryland, New Hampshire, Utah and Vermont—place restrictions on government or law enforcement use of ALPRs. Eight states limit how long data can be retained— ranging from 21 days in Maine to three years in Colorado. Florida, Maine, Maryland and Utah laws specify that ALPR data is confidential and exempt under public records laws.

Arkansas, Maine and New Hampshire also prohibit private use of ALPRs, with limited exceptions.

The Arkansas and Utah statutes, however, have been met with court challenges on First Amendment claims. Utah subsequently amended its law in 2014, removing restrictions on private sector use of ALPRs.

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