The rapid diffusion of license plate readers in US law enforcement agencies

The purpose of this paper is to document the diffusion of license plate readers (LPRs) in the USA, examining the variety, evolution and tracking of their uses through a national survey.

This study employs a national, stratified, representative survey of US law enforcement agencies with 100 or more officers.

LPR technology is currently used by at least two-thirds of larger police agencies, which represents a more than threefold increase in LPR acquisition in the last 10 years. The number of LPRs per agency, while small (about eight on average), has also more than doubled. Federal and state funding, advocacy by law enforcement leaders, and the intuitive appeal of LPRs have likely contributed to this rapid adoption. While LPRs are still primarily used to detect and recover stolen automobiles in patrol, their use has expanded into other types of investigative and security functions. Despite the increased use and numbers of LPRs in policing, their use is highly discretionary and infrequently tracked.

LPRs continue to be widely used in law enforcement, despite a lack of strong research evidence for their crime prevention benefits. Further studies are needed on the most effective ways for agencies to utilize small numbers of LPRs and the potential return on investment for acquiring larger numbers of the devices.

This study tracks the history of LPR diffusion and use and goes beyond prior law enforcement surveys by examining specific uses of LPRs and the extent to which agencies track their uses and outcomes.