The Impacts of Large-Scale License Plate Reader Deployment on Criminal Investigations

Published date01 September 2019
Date01 September 2019
Subject MatterArticles
untitled Article
Police Quarterly
The Impacts of
2019, Vol. 22(3) 305–329
! The Author(s) 2019
Large-Scale License
Article reuse guidelines:
DOI: 10.1177/1098611119828039
Plate Reader
Deployment on
Criminal Investigations
Christopher S. Koper1 and
Cynthia Lum1
The use of automated license plate readers (LPRs) has spread rapidly among
American police in recent decades. However, research on LPRs has been very lim-
ited and focused primarily on small-scale use of LPRs in patrol. This study expands
the evidence base on LPRs by evaluating investigative use of a large-scale fixed LPR
network in one populous city. Survival analysis methods were used to assess changes
in the likelihood and timing of investigative case closures in this city following instal-
lation of a fixed network of nearly 100 LPRs. The analysis focused on auto theft, theft
of vehicle parts, and robbery investigations, which account for most uses of LPRs by
investigators. Case clearances for auto theft and robbery improved after the instal-
lation of the LPR network, particularly in places where LPRs were concentrated.
However, these changes were not statistically significant in multivariate analyses, and
patterns in the data suggest that other factors may have also contributed to higher
clearances during the intervention period, particularly for auto theft cases. Results
suggest that large-scale LPR deployment may have the potential to improve investi-
gative outcomes for some serious crimes—particularly with more consistent use
and better placement for investigations—but further assessment is needed. More
generally, additional research is needed to determine the best uses of LPRs, the
1Department of Criminology, Law and Society, George Mason University, Fairfax, VA, USA
Corresponding Author:
Christopher S. Koper, Department of Criminology, Law and Society, George Mason University, 4400
University Drive, MS 6D12, Fairfax, VA 22030, USA.

Police Quarterly 22(3)
optimal scales and methods of LPR deployment, and the full range of costs and
benefits associated with LPR use.
license plate readers, police technology, criminal investigations, robbery, auto theft,
survival analysis
In recent years, police have increasingly sought to improve their efficiency and
effectiveness, especially in the investigation and clearance of crime, through the
use of new technologies. One relatively new surveillance and information-
gathering technology that has spread rapidly in American policing in the last
10 years is license plate recognition technology (Lum et al., 2018). Automated
license plate readers (referred to hereafter as LPRs) are high-speed camera and
information systems that read vehicle license plates in real-time (using optical
character-recognition technology), check them instantaneously against databases
with license plates linked to vehicles and persons of interest (e.g., stolen vehicles,
stolen license plates, and vehicles linked to wanted persons), and give automatic
alerts when matches are made. LPRs thus enhance the ability of police to detect
stolen vehicles and wanted persons in real-time. LPRs also record and store the
date, time, and location of scanned plates, which increases their value for a variety
of additional investigative purposes. Police have the option of installing LPRs in
police vehicles for mobile surveillance or setting them at fixed, strategic positions.
Given these capabilities, LPRs would seem to have considerable potential to
enhance patrol, investigative, and other security operations. Indeed, LPRs are a
very popular police technology and have been acquired by roughly two thirds of
large police agencies (100þ officers) in the United States (Lum et al., 2018).
However, research on the uses and impacts of LPRs is very limited. Prior studies
of LPRs, conducted in the United States and abroad, have focused largely on
demonstrating the accuracy and efficiency of the devices in scanning license
plates and their utility for increasing arrests, recoveries of stolen vehicles, and
seizures of other contraband (e.g., Cohen, Plecas, & McCormick, 2007;
Maryland State Highway Administration, 2005, pp. 58–83; Ohio State
Highway Patrol, 2005; Ozer, 2010; PA Consulting Group, n.d., 2004; Potts,
2018; Taylor, Koper, & Woods, 2011, 2012). In contrast, there is scant evidence
on whether LPR use actually improves investigative clearances or reduces crime
(Lum et al., 2018; Lum & Koper, 2017, pp. 120–124).
In practice, crime prevention and investigative outcomes from the use of
LPRs likely depend on several factors, including the volume of LPR

Koper and Lum
deployment, the manner in which LPRs are deployed (mobile vs. fixed), the
types of data accessed by LPR systems, how officers use LPRs in the field,
how LPR data are saved and used for investigations, and the public’s reaction
to (and influence upon) LPR use. Evidence on these issues is extremely limited,
however, as rigorous outcome evaluations to date have focused on small-scale
use of LPRs, primarily in patrol (Koper, Taylor, & Woods, 2013; Lum, Hibdon,
Cave, Koper, & Merola, 2011; Ozer, 2010; Potts, 2018; Wheeler & Philips,
2018). Accordingly, given the amount of resources spent on LPRs, there is
much need to build a stronger and broader evidence base on LPR applications
to inform police decisions about LPR adoption and uses.
To that end, this study examines the potential of large-scale LPR deployment
to improve criminal investigations. It is based on the experience of the
CMPD), which has nearly 100 LPRs deployed at dozens of fixed locations in
its jurisdiction. The study describes how CMPD investigators use LPRs for
various types of investigations and tests whether the installation of the LPR
network has improved the agency’s clearance rates for multiple types of crime.
The CMPD study adds to LPR evaluation research in multiple ways.
For one, it provides unique new evidence on the efficacy of LPR use for criminal
investigations. Police agencies are increasingly using LPRs to investigate a wide
variety of crimes beyond auto and license plate theft. Uses of LPRs now extend
to investigations of person and property crimes, missing and vulnerable persons,
gangs, vice, counterterrorism, and traffic and vehicle violations (Lum et al.,
2018). Yet, despite this trend, there has been little study of these investigative
applications of LPRs.1
The CMPD study is also notable in that it highlights fixed LPR deployment.
Although police most commonly mount LPRs on moving patrol cars, they
deploy about one-quarter of their units at fixed locations (Lum et al., 2018).
The relative advantages and disadvantages of fixed versus mobile deployment
have received little attention, as studies of LPRs to date have largely focused on
patrol use (for an exception, see Ohio State Highway Patrol, 2005). However,
fixed deployment may have advantages for many investigative applications
because it provides constant surveillance and a permanent record of vehicles
using selected roadways. Placed at strategic roads and intersections (e.g., roads
with high volume traffic in high crime areas), fixed LPRs may increase the
chances of detecting suspect vehicles, including those traveling to or from
crime scenes. This can prove valuable for real-time apprehension, follow-up
investigations, and other types of targeted investigations.
A final point is that the CMPD study attempts to quantify the effects and
value of large-scale LPR deployment. Currently, most agencies using LPRs
possess only a small number. Even among large agencies that own LPRs,
three-quarters own fewer than 8 units, 90% own less than 15, and only 5%
own more than 25 (Lum et al., 2018). Nonetheless, the numbers of LPRs owned

Police Quarterly 22(3)
by agencies has been growing, and many agencies plan to expand their LPR
acquisition (Lum et al., 2018). In principle, expanding LPR deployment should
increase its potential impacts for patrol and investigations, but further evalua-
tion is needed to guide agencies on the value and cost efficiency of making larger
investments in this technology.2
Study Site and Context
Charlotte-Mecklenburg is a consolidated city-county jurisdiction with a popu-
lation of roughly 1 million people covering about 546 square miles.3 The core of
the jurisdiction is the city of Charlotte, which has nearly 800,000 residents.
The CMPD, an agency with about 2,000 sworn officers and 2,400 total employ-
ees, is responsible for policing most of the jurisdiction. In 2016, the CMPD
investigated approximately 6,600 violent crimes and 36,700 property crimes
based on UCR Part 1 offenses.4
LPR History and Capabilities
At the time of this study, the CMPD had 95 LPRs located at 44 fixed positions
throughout the city, each of which typically had multiple LPR units covering
different sides, directions, and portions of the location’s roads and intersections.
The agency had 14 additional units that were mostly mounted on mobile trailers
or patrol vehicles. The CMPD acquired most of these LPRs in 2012 with federal
funding to provide additional security for the Democratic National Convention
(DNC), which was held in Charlotte-Mecklenburg in September of that year.
Because the LPR network was initially installed to meet security concerns for
this convention, the LPRs were largely concentrated on key roadways in the
city’s downtown and in other central areas. At the time of this study, the fixed...

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