Having a valid driver’s license might not alter undocumented migrants’ likelihood of being involved in a car accident unless acquiring a license affects how much they drive or the quality of their driving. Yet, being licensed might lower undocumented migrants’ propensity to flee a serious car accident scene. Irrespective of who is at fault, unlicensed undocumented migrants might fear encountering law enforcement since lacking a driver’s license and insurance may result in a criminal conviction and deportation. If undocumented migrants are authorized to drive, they might be more likely to be insured and more inclined to stay in the accident scene, which is particularly relevant in the case of serious accidents as it can save lives when they seek the assistance of first responders. We investigate the validity of that hypothesis, focusing on the most extreme cases of hit and run accidents, namely fatal accidents.

Using data on the universe of fatal car accidents in the United States, we examine changes in the share of fatal accidents that are hit and runs, as well as changes in the number of fatal hit and run accidents per 100,000 people (i.e., its numerator) and the number of fatal accidents per 100,000 people (i.e., its denominator),1 following the extension of driving privileges to undocumented immigrants. We find that issuing undocumented migrants driver’s licenses does not significantly alter the rate of fatalities; however, it lowers the share of hit and run fatalities anywhere between 20 percent and more than 50 percent, depending on the estimation methodology employed. The findings are not the byproduct of reverse causality, nor are they driven by confounding population changes. As such, the results suggest that extending driving privileges to undocumented migrants reduces the share of fatal accidents in which drivers flee the scene. Notably, the policy’s impact is not driven by overall improvements in traffic safety, as the number of fatalities per 100,000 does not significantly change. Rather, it is the reduction in the number of fatal hit and runs that lowers the share of fatal accidents in which some involved driver(s) flee the scene.

Our findings contribute to the literature on immigration policy examining the impacts of extending driving privileges to undocumented migrants. Prior studies have evaluated how issuing driver’s licenses to undocumented migrants affects their labor market outcomes (Barajas, 2021; Amuedo-Dorantes et al., 2020), car ownership (Cho, 2022), commute patterns (Amuedo-Dorantes et al., 2020), and car insurance (Churchill et al., 2021; Cáceres and Jameson, 2015). We focus, instead, on the impact of such a policy on public safety as captured by traffic fatalities. In a related study, Lueders et al. (2017) explore how granting driving privileges to undocumented migrants in California impacted the state’s traffic safety during the one-year period immediately following the policy adoption. The authors use the predicted number of issued permits and the number of hit and run accidents in each county to show that counties with a higher share of newly issued licenses exhibit a larger reduction in the share of hit and run accidents in the short run.

Using data on the entire universe of fatal car accidents in the United States, we revisit the public safety implications of issuing driver’s licenses to undocumented immigrants. Our analysis makes three important contributions. First, it provides an extended geographic scope, increasing the ability to extrapolate the findings beyond the state of California. Second, it covers a 30-year period, enabling the assessment of the short- and long-run impacts of the policy. Finally, it addresses important concerns regarding the potential for two-way fixed effects (TWFE) estimates to be significantly biased in the presence of a staggered policy treatment (Goodman-Bacon, 2021), as was the case with this policy.

Understanding the diverse impacts of extending driving privileges to undocumented immigrants is particularly relevant in the current policy context, as states continue to debate whether to adopt such measures. In 2022, Rhode Island became the most recent state to enact legislation extending driver’s licenses to undocumented immigrants (SB 2006/HB 7939). In addition, Massachusetts voters elected to uphold a bill allowing those without proof of lawful presence to obtain driver’s licenses (SB 4822/HB 4805), which had been vetoed earlier by the governor. Thus, an updated assessment of how these policies impact public safety beyond California in the short- and long-run is well warranted.

Institutional Background

The debate surrounding who should be eligible for a driver’s license is not new. Since automobiles became the preferred mode of transportation at the beginning of the 20th century, state legislatures enacted driver’s license laws to make sure drivers would learn traffic rules regardless of their immigration status. On the premise that having properly trained, tested, and identified drivers would promote public safety, insurance companies requested drivers to be licensed to ensure they would know traffic laws and to maximize the pool of those insured (Johnson, 2004). Similarly, some law enforcement agencies endorsed the idea of licensing as many drivers as possible to encourage cooperation with police and discourage hit and runs when people lacked a license.2 However, the meaning of driver’s licenses changed as they became the primary form of identification and effectively operated as national identification cards. Denying access to a driver’s license amounted to depriving individuals from the ability to rent an apartment, open a bank account, get a job, and identify oneself in federal, medical, and educational institutions. Because, in addition to their public safety implications, driver’s licenses became a necessity to function in American society, most states permitted undocumented migrants to obtain a driver’s license before the 1990s.

Nevertheless, states changed their practices following the September 11, 2001 terrorist attacks. Some of the non-citizen hijackers had boarded the planes using driver’s licenses. As a result, fears of identity fraud started to dominate the debate regarding the granting of driver’s licenses to undocumented immigrants (Silva, 2015), and many states tightened their rules for issuing driver’s licenses. In addition, four years later, Congress passed the REAL ID Act of 2005. This legislation effectively ended some of the discordance that predated 9/11, with some states requiring the presentation of birth certificates and social security cards for issuing driver’s licenses and others requiring no proof of legal residence at all. The 9/11 Commission suggested that states required future applicants of driver’s licenses to present some documentation of their legal status. As a result, by the early 2000s, most states restricted undocumented migrants’ access to driver’s licenses by requesting a social security number or proof of legal status to issue a driving permit (Pew, 2016).

States’ practices started to shift, once more, around 2012, coinciding with the intensification of interior immigration enforcement impacting entire mixed-status households. Concerns that undocumented migrants would still drive when lacking a license,3 evade renewing expired licenses, and fail to integrate into society4 led to an increased support for granting undocumented migrants access to driver’s licenses or, more accurately, permits.5 While the rationale for enacting these policies varied across states, it often included potential economic gains (more people able to drive to work), improved public safety (more people passing driver’s education and tests and being required to purchase car insurance), and the hopeful containment of car insurance premiums (Gonzalez and Margulies, 2017). In 2023, a total of 19 states grant some type of driving privilege to undocumented migrants (see Appendix table A.1).

Related Literature

Several authors have examined the implications of expanding driving privileges to undocumented migrants. One of the earliest studies is by Cáceres and Jameson (2015), who underscore some of the public safety benefits of issuing driver’s licenses to undocumented immigrants described earlier. Specifically, the authors note that lack of proper training, testing, and car insurance can result in more accidents and higher insurance costs.6 Follow-up studies have further noted how extending driving privileges to undocumented migrants does not increase the cost of insurance (Lueders and Mumper, 2022), does not raise car ownership (Cho, 2022), and keeps the number of drivers unchanged (Churchill et al., 2021), suggesting that some undocumented migrants were previously driving without authorization. Other analyses have also shown benefits pertaining to labor market gains. For instance, Barajas (2021) shows how granting driver’s licenses to undocumented immigrants increases their mobility and commuting times, and in consonance with this finding, Amuedo-Dorantes et al. (2020) and Cho (2022) document a simultaneous growth in job opportunities and hours worked.

In this study, we focus on yet another externality of granting driver’s licenses to undocumented migrants – namely, their ability to lower the likelihood of hit and runs in the case of serious accidents where lives are at risk. Unlicensed drivers are more likely to leave the scene of a fatal accident; 15 percent of these drivers do relative to 1.7 percent of licensed drivers (AAA Foundation for Traffic Safety, 2011) as driving without a license is a traffic offense that may result in a criminal conviction. Having multiple criminal offenses on record, including an illegal entry or reentry, can lead to deportation. Hence, undocumented migrants might be particularly fearful of a police encounter and in turn be more likely to flee an accident scene. In that spirit, Wong et al. (2019) show how undocumented migrants are over 40 percent less likely to report a crime to the police, even when they were the victims, if they believe law enforcement cooperates with U.S. Immigration and Customs Enforcement.

Of particular interest to us are the findings by Smith et al. (2021), who analyze the “traffic stop-to-deportation pipeline” in New York using U.S. Customs and Immigration Service data available through Syracuse University’s Transactional Records Access Clearinghouse system. They document that many deported migrants are apprehended during traffic stops despite having no criminal convictions. Focusing on a sample of drivers caught by the police after fleeing the accident scene, Solnick and Hemenway (1995) further note that many are younger male drivers who drive at night and fear severe punishment. Benson et al. (2021) confirm those traits and further show how the share lacking a driver’s license is larger in hit and runs (30 percent) than in other car accidents (10 percent). Finally, focusing on California, Lueders et al. (2017) show that, following the expansion of driving privileges to undocumented migrants, hit and runs drop the most in counties with more issued driving permits, suggesting these drivers are now less likely to flee an accident scene.

We contribute to this literature with an analysis of how granting driving privileges to undocumented migrants might impact traffic safety as captured by hit and run fatalities. Unlike prior studies, we rely on the universe of fatal car accidents in the entire United States over the past 30 years. The expanded temporal and geographic coverage enables us to gauge the short- and long-run impacts of this type of policy beyond California, improving the ability to extrapolate the findings. In addition, we pay attention to the staggered adoption of the policy, which could result in biased TWFE policy estimates. Overall, the findings allow us to assess if, as argued by proponents of expanding driving privileges to undocumented migrants, this type of policy improves traffic safety, as captured by the share of hit and run fatalities or generates a “call effect,” possibly raising the number of drivers and traffic hazards. While there is some evidence of undocumented migrants responding to heightened immigration enforcement by leaving the state (Bohn et al., 2014; Watson, 2013), their mobility response to the expansion, or lack of, driving privileges has not been assessed yet. We address that concern in our identification checks and, overall, evaluate which argument is supported by empirical evidence.

Data and Descriptive Statistics

Our primary source of data is the 1990–2019 Fatality Analysis Reporting System (FARS) published by the National Highway Traffic Safety Administration. It contains a census of fatal traffic accidents involving a motor vehicle and resulting in at least one death within 30 days of the crash. The data contain information on the location, the type of accident, and whether it involved a hit and run. If the driver remained at the scene, the state issuing the driver’s license is documented. In the case of hit and run fatalities, we know the location of the accident but lack data on the state issuing the driver’s license. Yet, to our knowledge, there is no evidence of out-of-state drivers being more likely involved in hit and runs than other drivers.7

The FARS data also include characteristics of the crash, such as the time of the day, day of the week/month, and weather conditions. Following the existing literature, we construct controls for weekend, nighttime, and low-visibility conditions. To address the procyclical nature of traffic accidents (Ruhm, 2015) and their association with alcohol consumption (Cotti and Tefft, 2011), we also gather and merge monthly unemployment data. Additionally, we account for whether the state is a sanctuary state based on its adoption of a Trust Act policy (see Appendix table A.2) as well as for the immigration climate in the state through an index constructed using the information on various immigration enforcement policies in place in the state (see Appendix table A.3). Our key regressor is a dummy variable indicative of when the state expanded driving privileges to undocumented migrants, as detailed in Appendix table A.1. For identification purposes, we exploit the temporal and geographic variation in the adoption of such state-level measures.

Because undocumented migrants are geographically clustered, we focus on states where the policy might have had a greater impact, namely states with a larger share of this demographic. To identify those states, we construct shares of likely undocumented migrants in each state. We use data from the 1990 Census to capture the undocumented population before the sample coverage period and before any state expanded driving privileges to avoid changes in the undocumented population as a result of the policy adoption. Given the composition of the likely unauthorized population in the United States in 1990, we consider citizenship, country of origin, and educational attainment as traits highly predictive of unauthorized immigration status (e.g., Mexican noncitizens with less than a high school education), in combination with the residual approach used by Borjas (2017).8 Our focus is on states with a share of 0.4 percent or higher, although the results prove robust to using alternative thresholds.9

Figure 1 presents the states with a high share of likely undocumented migrants in darker shades. These are the states where the policy might have an identifiable impact given its targeted population. The map further distinguishes (line pattern) states that expanded driving privileges to undocumented migrants (i.e., our treated group constituted by California, Illinois, Nevada, and New Mexico) versus states that did not (i.e., our control group, which includes Arizona and Texas).