In 2015, the global revenue from cell phone sales was in excess of $400 billion United States’ (U.S.) dollars [1]. More than 90% of U.S. residents possess a cell phone subscription [2] and over 60% of these subscribers owns a smartphone [3], which enables users unfettered access to information and communicative abilities such as calling, texting, emailing, and video chat. A 2015 national survey of cell phone owners revealed that nearly 50% of respondents said they could not live without this technology [2]. Therefore, there is little controversy that many Americans are enamored with their mobile devices.
While cell phones permit users with a constant connection to their environment and social circles, they also can serve as a constant distraction. National surveys suggest that many do not refrain from using this technology even in situations that may be hazardous, such as driving [4, 5]. There is a substantial body of literature that is comprised of experimental, epidemiologic, and naturalistic studies, which show cell phone use while driving (CPWD) negatively affects driving ability as it likely interferes with a driver’s visual, manual, and cognitive function [6,7,8,9]. Because the behavior is prevalent [10, 11] and has been increasing [11, 12], CPWD presents an enormous challenge for traffic safety and public health. Some have suggested that this may be due to the fact that perpetual cell phone use is a social norm [13].
As part of the federal government’s strategic plan to end CPWD, the U.S. Department of Transportation has actively encouraged states to pass CPWD legislation [14]. Consequently, states have ratified a myriad of CPWD laws consisting of bans on hand-held CPWD, texting while driving, and any cell phone use by young drivers (i.e. young driver all cell phone bans). As of October 2016, 14 states have enacted hand-held CPWD bans applicable to all drivers, 46 states have passed texting while driving bans for all drivers, and 37 states ban any type of cell phone use for young or inexperienced drivers (i.e. those with learner’s permit or intermediate licenses) [15].
Various studies have investigated the effectiveness of CPWD laws on reducing collision claims, fatal/injurious crashes, hospitalizations, road-side observed and self-reported CPWD behavior [9]. Because this study focuses on road-side observed driver behavior, only these types of studies shall be reviewed. To the authors’ knowledge, seven studies have scrutinized the effectiveness of CPWD bans on road-side observed driver behavior [16,17,18,19,20,21,22]. Two of these studies investigated the short and long term effects of a young driver all cell phone ban on phone usage among teenage drivers in North Carolina [17, 18]. In the first study, teenage drivers were observed one to 2 months before and then 5 months after the law passed [17]. The second study assessed the longer-term effects of these laws by observing teenage drivers at the same high schools originally sampled, but 2 years after the law’s implementation [18]. The first study found that the law had minimal short-term effects on driver phone usage [17]. In the second study, hand-held cell phone conversations occurred less overall, but the authors’ attributed this to the fact that texting was likely replacing talking on hand-held cell phones [18]. In regards to driver sex, these authors noted that female teen drivers were >60% more likely to talk on phones than males both before and after the law was passed [17, 18]. As for hand-held bans and road-side observed driver phone usage, five studies have explored this relationship [16, 19,20,21,22]. Four studies conducted by the Insurance Institute for Highway Safety investigated the short and long term effects of driver hand-held CPWD bans in Washington, DC and several New York and Connecticut communities [19,20,21,22]. In New York, hand-held CPWD initially decreased after the ban was enacted and then rose to pre-law levels 16 months later; the findings also showed that CPWD decreased among both sexes and across various age groups of drivers (i.e. <25, 25–59, and 60 year old drivers) [19, 20]. In Washington, DC, driver hand-held CPWD was greatly reduced both immediately after and for a year after the ban was ratified [21, 22]. In Connecticut, driver hand-held phone use was greatly reduced both immediately after and for almost 3.5 years after the passage of the law [22]. Only one study investigated road-side observed hand-held CPWD in a nationally representative sample of drivers between 2004 and 2010 using a difference-in-difference approach [16]. It appeared that hand-held bans were associated with decreased road-side observed hand-held CPWD; this relationship was consistent among drivers aged 16–24 and ≥25 years [16].
Collectively, these studies suggest that hand-held CPWD bans likely reduce road-side observed cell phone use among drivers. However, there are still extant gaps in the literature. It is not completely clear whether these cell phone laws are associated with reduced cell phone use behavior across different sub-groups of drivers, such as different ages, sexes, races/ethnicities, or even by location, such as rurality or region. Most of these studies did not formally test for sub-group differences. National surveys show that self-reported cell phone use varies by activity (i.e. if the person is calling, texting, emailing, viewing internet/apps, etc.) and also by age, sex, race/ethnicity, and rurality [23]. For example, texting behaviors do not differ by sex, but varies inversely with age, is less common in rural areas, and is more common among African Americans and Latinos compared to White Non-Hispanics [23]. National self-reported surveys of drivers reveal female drivers tend to text and have hand-held cell phone conversations less than males, and that both texting and hand-held phone conversations typically decrease as driver age increases [24]. Contrarily, road-side observed surveys of drivers from 2005 to 2014 show that females have consistently used hand-held phones to converse while driving more than males [10]. Research concerning other traffic safety laws has also shown that laws are not always equally obeyed amongst population sub-groups. It is well-established in the literature that younger drivers and males typically engage in riskier driving behaviors and receive more traffic citations, particularly when it comes to seat belt use, speeding, or driving too fast for conditions compared to females or middle-aged drivers [25, 26]. Race and ethnicity are often varied in fatal crashes concerning alcohol, seat belt non-use, and speeding [27] or with reciving traffic citations [28]. Previous studies have also shown that rural drivers tend to speed, not wear safety belts, and run stop signs/lights more than urban drivers [29, 30].
Because of these reported differences, the objective of this study was to investigate the association between hand-held CPWD laws and road-side observed hand-held cell phone conversations across driver sub-groups and regions. Because texting bans and young driver all cell phone bans may also influence driver behavior, this study controlled for these other bans. Given the existing research, it was hypothesized that universal hand-held bans may be associated with lower cell phone use in some driver sub-groups and regions. Determining this information is important for the development and tailoring of future public health interventions and/or public safety campaigns regarding hand-held cell phone use while driving.