NIJ - National Institute of Justice
NIJ - National Institute of Justice
03/09/2024 | Press release | Distributed by Public on 03/09/2024 22:10
Alternative Traffic Enforcement: Identifying Areas for Future Research
Alternative traffic enforcement is an emerging crime and justice issue prompted by efforts of dozens of jurisdictions throughout the United States. In response to documented dangers and disparities, they seek to change how some traffic violations are handled.[1] Specifically, these strategies try to increase public safety and reduce demands on officers by deprioritizing some traffic offenses and shifting enforcement responsibilities to alternative agencies or technologies. Most of these programs are in their infancy. Few have documented outcomes or formal evaluations to assess their effectiveness. As a result, there is little information about the potential impact of recent initiatives on public and officer safety, disparities, and other important outcomes, which provides a fundamental research opportunity.
This article provides an overview of the current state of alternative traffic enforcement practice and discusses opportunities for future research. By informing the field about this critical but understudied topic, we hope to encourage further examination and promote cutting-edge research as well as evidence-based policies and practices. The article first describes the issue and current state of U.S. alternative traffic enforcement strategies, highlighting challenges in measuring disparities. We then provide a summary of documented alternative traffic enforcement reforms, initiatives, and related research. The article closes with a description of future research opportunities.
The Current State of Alternative Traffic Enforcement
Traffic stops are the most common reason people encounter police,[2] and data suggest that officers spend substantial time on traffic enforcement.[3] Several studies show that traffic stops and searches are associated with reduced motor vehicle crashes, injuries, and fatalities.[4] However, traffic stops can pose risks for the public and the police, and specific traffic enforcement strategies may perpetuate criminal justice contact disparities.[5]
Risks like these have caused some researchers to examine traffic stops. Although low-level traffic stops sometimes reveal more serious crimes, such as those involving drugs or weapons, data indicate they infrequently lead to discovered contraband.[6] Some studies find that limiting low-level traffic stops can be associated with fewer traffic crashes and could increase arrests for more serious traffic offenses, such as a DUI.[7] Reducing stops is not associated with increases in serious crime. Policy changes, such as deprioritizing investigative stops, have been linked with reduced assaults on police officers.[8]
Traffic encounters can be dangerous for police. Traffic-related deaths are a leading cause of officer fatalities, although some deaths may not relate to traffic stops. In 2023, five officers were killed in firearm-related incidents during traffic enforcement, and another 37 officers were killed in crashes or vehicle impacts. This accounts for almost a third of the 136 officer fatalities that year.[9]Beyond firearm-related deaths, the data do not distinguish which officer deaths result from traffic stops. Additionally, it is unknown how many motorists and officers are injured during traffic stops each year.
Police conduct more than 20 million traffic stops per year.[10] Although most traffic stops end without incident, recent high-profile deaths of Black motorists following traffic stops have prompted calls for reform.[11] In 2023, a total of 109 people were killed by police after being stopped for traffic violations.[12] Available data indicate that Black people were disproportionately killed by police compared to their share of the population. Although Black people were 12% of the population, 24% of individuals killed by police were Black in 2023. (This data does not indicate how many deaths were related to traffic stops.)
Racial disparities have been documented in traffic stops. This is exemplified by the community-developed terms "driving while Black" and "driving while brown," which describe non-white motorists' personal experiences of racial profiling in traffic stops.[13]
Several studies validate this experience, finding that Black motorists are more likely to be pulled over than white motorists.[14] Research also finds that Black and Hispanic motorists are more likely to be searched compared to their white counterparts.[15] Although non-white motorists are searched more frequently, multiple studies find that the "hit rate"- the odds of finding contraband - is the same or lower than the hit rate for white motorists. Lower hit rates for non-white motorists have been interpreted as evidence of racially biased motivation for traffic stops. Racial bias interpretations are also supported by findings that Black male drivers are more likely to be involved in stop-related searches that do not lead to an arrest.[16]
However, estimating disparities is complex. Studies use different methods to test for bias, making it difficult to discern disparities on a large scale or across studies and jurisdictions.[17] Some data and research studies suggest bias, but findings are mixed.
Challenges in Measuring Disparities
Recent traffic enforcement research attempts to overcome previous methodological shortcomings in measuring racial disparities. However, few evaluations rigorously measure the impact and effectiveness of alternative traffic enforcement programs, procedures, and policies on safety or disparities.
Some past research has documented disparities in traffic enforcement, but methodological and sample variations, coupled with limitations in estimation techniques, offer an incomplete understanding of systematic bias.[18]
One of the missing pieces is how traffic stop disparities are measured. Commonly used estimation methods involving population benchmarks or hit rates may fail to consider relevant factors in police contact and officer decision-making.[19]For example, methodologists note that using underlying population statistics (e.g., determining racial distributions based on inhabitants' residential addresses) does not accurately reflect who is at risk of being stopped and distorts risk estimations across groups. This impacts the accuracy of conclusions concerning officer bias. Additionally, behavior such as a motorist's demeanor is not captured in data but can influence officer search decisions, further distorting bias estimations. In practice, inaccurate or incomplete statistics and data can generate inaccurate disparity estimations[20] Further, prior research fails to adequately examine why identified disparities exist.[21]
Recent research to address previous methodological concerns has sparked further debate. For example, Grogger and Ridgeway's "veil of darkness" (VOD) hypothesis argues that bias can be detected if drivers' race distribution is different after sunset than during the day, which is when a motorist's race is easier for officers to discern.[22] Comparing the racial distribution of daytime stops to nighttime stops may avoid population benchmark problems. Using variations of the VOD hypothesis, two single-site studies report little evidence of traffic stop racial bias,[23] while one large-scale study (with data from nearly 100 million traffic stops in 21 states) finds the opposite.[24] Differences in sampling strategies may account for the mixed findings.[25] Recently, researchers funded by the Bureau of Justice Statistics developed a new quantitative method to test the VOD hypothesis that incorporates several considerations including providing a weighting method to account for seasonal driving patterns. When applying this method to an analysis of 50,000 traffic stops conducted by Michigan State Police in 2021, results suggests that stops conducted in daylight were more likely to involve Black drivers.[26]
Several U.S. localities have instituted alternative traffic enforcement strategies to reduce police resource burdens while also addressing racial disparities and negative public safety outcomes. We describe several of these efforts below.
Traffic Enforcement Reforms and Initiatives
Common alternative traffic enforcement strategies include deprioritizing minor traffic violation enforcement, shifting enforcement responsibilities to unarmed civilians, and using technology like red light cameras in lieu of in-person enforcement. New policies are often implemented with little to no research evidence to support changes; they may face challenges legislatively and with implementation. We reviewed policies and programs around the country and highlight examples below.[1] See Table 1 for all reviewed policies and programs. (Policy searches were conducted in summer 2023 and updated as of spring 2024. The results do not constitute a formal evaluation of all policies.)
- Implemented but not evaluated:On June 22, 2021, the Portland (Ore.) mayor and police chief issued directives to de-prioritize traffic stops for some low-level traffic violations, such as expired registrations.[27] Additionally, they instructed police officers to modify their search protocols to allow for informed consent. Officers must create audio recordings of their interactions, specifically explain that drivers can refuse a search, and hand out cards that explain a driver's rights. Although the Portland Police Bureau publishes quarterly traffic stop data, there does not appear to be an official evaluation of the policy.[28]
- Passed and challenged: In 2021, the mayor of Philadelphia (Pa.) issued an executive order detailing driving equality reform, which de-prioritized certain low-level traffic offenses, such as expired registrations and inoperable light violations.[29] The reform also required the police department to report information on stops, including demographic data. In February 2022, the Philadelphia Lodge of the Fraternal Order of Police sued the city to invalidate this order, arguing it attempts to preempt state laws.[30] As of February 2023, the suit was still ongoing.[31] In November 2022, an arbitration panel determined the city could create an unarmed traffic enforcement unit.[32]In March 2023, the city established the first civilian public safety unit;outcomes have yet to be reported.[33]
In addition, scholars and advocates argue for programs and policies that do not directly involve the police. They believe these changes can improve traffic safety while decreasing police interaction. These strategies may be used alone or in conjunction with other alternative traffic programs, but racial equity has been identified as a primary concern.[34] These include:
- Enhancing infrastructure, street design, and public transit.[35] Improving traffic infrastructure, such as making necessary roadway repairs or building roundabouts, and public transit efficiency and accessibility may reduce traffic crashes without police intervention. Complete Streets and Vision Zero are two programs that focus on the traffic system, rather than individual motorists' behavior, by designing better functioning roadways. Complete Streets policies have been adopted in several jurisdictions, such as El Paso and New Orleans.[36] Vision Zero has been instituted in communities across various states, including Boston, Chicago, and Los Angeles.[37]
- Addressing financial penalties associated with traffic violations.[38] Traffic stops are a source of revenue produced by fines levied on motorists who commit moving violations and other traffic related infractions. Removing financial incentives for police to conduct traffic stops could reduce officer interactions with the public, thereby reducing incidents resulting in unjustified or excessive use of force.
Evaluated Programs
Formal evaluations of alternative traffic enforcement strategies are still emerging, but some research on existing programs and technologies is available. We summarize these studies below.
- In 2013, the Fayetteville (N.C.) Police Department was one of the first police departments to reprioritize traffic stops to focus on safety while de-emphasizing regulatory traffic stops.[39] A 2020 study concluded that policy changes were associated with reductions in vehicle crashes, traffic-related injuries/fatalities, and racial disparities, with no increase in non-traffic crimes.[40]Traffic stop disparities were measured by: (1) percent of Black non-Hispanic stops and (2) the rate ratio of Black non-Hispanic to white, non-Hispanic traffic stops.The ratio was adjusted by statewide estimates of vehicle access and miles traveled per year by race/ethnicity to avoid the methodological issues of using the residential population alone. A 2023 study found these policy changes were associated with reduced assaults on officers.[41]
- The Seattle (Wash.) police chief issued a memorandum in 2022 removing several low-level violations as primary reasons to initiate a traffic stop, including cracked windshields or items hanging from the rearview mirror.[42] In 2023, researchers evaluated the policy's impact on DUI and drug crime incidents. They found no statistically significant reductions in either type of incident following implementation.[43] This suggests that policy changes did not result in these offenses going undetected by police. The study did not include an analysis of racial disparities.
- In 2021, the Ramsey County (Minn.) Attorney's Office issued a policy to cease prosecuting felony cases that originated solely from traffic stops for low-level offenses unrelated to public safety. These included those for vehicle light violations or expired registrations.[44] The St. Paul Police Department supported the policy and advised officers not to initiate traffic stops solely for minor violations. Recent data analysis from the Justice Innovation Lab indicates that Ramsey County stops for low-level traffic violations decreased while stops for more serious traffic offenses (including speeding and DUI) increased. [45] While racial disparities in stops and searches for vehicle equipment violations declined, Black drivers still experienced the highest rates of both. Rates were calculated using the entire county population of each group rather than only those of driving age. This method has been called into question by some researchers because it may not accurately reflect disparities by including the population of non-drivers.[46] Disparities could be under- or overstated, depending on the makeup of the driving population.
- Red light and speed cameras represent technological alternatives to some types of traffic enforcement. Their impact has been evaluated, including systematic literature reviews. Red light cameras have been associated with increased rearend crashes but reduced red light violations and other types of traffic crashes, including right angle crashes.[47] Speed cameras were found to reduce traffic injuries and deaths; however, without rigorous evaluation, the magnitude of these impacts is unclear.[48] Although these technologies may seem outwardly race neutral,[49] their impact on disparities is not well understood. Some areas report disproportionate ticketing in Black and Latino communities.[50]
Opportunities for Future Research
This paper shows how research demonstrates the potential dangers present in traffic stops, but few evaluations measure the impact of alternative traffic strategies on public safety or disparities. Such rigorous evaluations are needed to understand whether these programs achieve their objectives or generate unintended consequences.
The need to measure the racial disparities in traffic stops has grown particularly urgent. Many recently implemented reforms were prompted by calls to reduce racial disparities among those stopped, searched, and arrested. Rigorous evaluations should include all alternative programs, including red light and speed cameras.
The research community also needs new, innovative, and more accurate ways to measure traffic enforcement disparities as well as greater consensus about how to best account for different levels of risk or exposure to police stops by age, race, ethnicity, and sex. Current research includes a variety of ways to measure risk, making it difficult to compare results across studies. Theoretical concepts like the veil of darkness could be further specified to ensure proper testing of hypotheses and comparability across studies.
It is important to also have consistent, comparable studies that examine how new traffic enforcement policies and practices impact officers, particularly officer safety. Researchers have opportunities to further assess the impact of traffic policy changes on police operations, cost, and officer productivity. Although some police departments are shifting traffic enforcement to nonsworn staff, additional research can address the impact of such policies on both the unarmed, nonsworn responders and the public.
Evaluation of policies related to traffic enforcement could expand beyond traditional law enforcement policies. For instance, in July 2023, Maryland passed a bill which prohibits specific types of cannabis-related evidence to be used as the sole basis for establishing reasonable suspicion or probable cause.[51] Clear disparities in statewide traffic stop data led to the passing of the bill, and its goal is to decrease the volume of investigative stops as well as warrantless vehicle searches. However, in early 2024, a new bill was introduced to eliminate these protections for motorists. This type of policy change and its associated debates should also be considered part of the conversation regarding alternative traffic enforcement.
NIJ plays an important role in this research. Since fiscal year (FY) 2018, NIJ has funded over $3 million in research related to traffic stops or traffic safety. Due to the continued need for more rigorous research and evaluation on these policies, NIJ released a solicitation for funding in this area for FY24 (Research and Evaluation on 911, Alternative Hotlines, and Alternative Responder Models).[52] With this solicitation, NIJ sought proposals to assess the impact and benefits of alternative traffic enforcement models. Awards are forthcoming.
Table 1: Alternative Methods of Traffic Enforcement in PracticeNote: The table represents results from review of policy searches conducted in summer 2023 with status updates as of spring 2024. Although it includes data on traffic stops and enforcement for some localities, the results do not constitute a formal evaluation of all policies. NIJ librarians and science staff completed all searches.