Distracted driving

Using a cellphone while driving increases crash risk. Researchers have consistently linked texting or otherwise manipulating a cellphone to increased risk. Some studies, but not all, have found that talking on a cellphone also increases crash risk.

Cellphones and texting aren’t the only things that can distract drivers. The National Highway Traffic Safety Administration defines distracted driving as any activity that could divert attention from the primary task of driving. Besides using electronic gadgets, distractions can also include adjusting a radio, eating and drinking, reading, grooming, and interacting with passengers. The crash risk associated with these other activities isn't well established.

Laws restricting phone use by drivers and crash avoidance technology are two approaches that may help reduce distraction-related crashes. Broad bans on manipulating electronic devices seem to be most promising, rather than laws that only target talking or texting. Crash avoidance systems can bring drivers’ attention back to the road, regardless of the cause of the distraction.

A 2021 national observational survey found that 2.5 percent of drivers stopped at intersections were talking on hand-held phones at any moment during the day (National Center for Statistics and Analysis, 2022). Combining this observational data with self-reported data on hand-held and hands-free phone use, the federal government estimates that 7.6 percent of drivers were using a hand-held or hands-free cellphone during any moment of the day.

In the same survey, 3.4 percent of drivers were observed manipulating hand-held devices or infotainment systems. The rate was highest, at 5.4 percent, for drivers estimated to be 16-24 years old.

In a recent IIHS survey of US drivers, over a fifth of respondents reported engaging in at least one smartphone-based distraction, such as making video calls, watching videos or using social media, on most or all of their trips (Cox et al., 2022).  

People who use cellphones more frequently while driving may be riskier drivers in other respects. In an IIHS study of drivers who were continuously monitored for one year, the drivers who spent the greatest amount of their driving time interacting with a cellphone also had the highest rates of near crashes and crashes (Farmer et al., 2015). In an on-road study, drivers who reported frequent cellphone use drove faster, changed lanes more often and made more hard braking maneuvers than drivers who said they rarely used cellphones while driving (Zhao et al., 2013).

There are no reliable estimates of the number of crashes caused by distracted drivers. Most of what we know about cellphones and crash risk comes from naturalistic studies. Such studies have consistently linked texting or otherwise manipulating a phone to increased risk. There is mixed evidence about whether talking on a cellphone increases crash risk.

Based on national police-reported data on fatal crashes in the United States during 2021, 3,522 people died in motor vehicle crashes in which distraction was deemed a contributing factor. That is 8 percent of all crash deaths. Of that number, 377, or less than 1 percent of people killed on the roads, died in crashes involving cellphone use.

Statistics based on police-reported crash data almost certainly underestimate the role of distraction in fatal crashes. Police crash reports aren’t a reliable way to count cellphone-related collisions because drivers often don’t volunteer that they were on the phone and there is usually a lack of other evidence to determine drivers’ phone use.

Data from over 3,000 drivers who were continuously monitored for up to 3 years during 2010-13 have been used for several studies of the effect of cellphone conversations. Three of these (Dingus et al., 2016; Kidd & McCartt, 2015; Guo et al., 2016), including one by IIHS researchers, found that talking on a cellphone significantly increased crash risk compared with periods when drivers were not visibly distracted, although the risk was limited to drivers 16-29 in the third. In contrast, other analyses of the same data found that talking on a hand-held cellphone did not significantly increase crash risk (Dingus et al., 2019; Owens et al., 2018). This finding is consistent with an earlier IIHS study of cellphone use by 105 drivers during a one-year period (Farmer et al., 2015).

The evidence is clearer when it comes to texting or manipulating a cellphone. The publications from the naturalistic study of over 3,000 drivers indicated that crash risk was 2-6 times greater when drivers were manipulating a cellphone compared with when they were not distracted (Dingus et al., 2016; Kidd & McCartt, 2015; Owens et al., 2018). When looked at by age group, there was a significant increase in crash risk for drivers under 30 years old and drivers over 64 (Guo et al., 2016).

Nearly all experimental studies using driving simulators or instrumented vehicles reported that some measures of driver performance were affected by the cognitive distractions associated with cellphone tasks (McCartt et al., 2006). Statistical analyses aggregating the results of multiple studies reported significant delays in drivers’ reaction time but little or no effect of cellphone conversations on lane keeping, speed or following distance (Caird et al., 2008; Horrey & Wickens, 2006).

An analysis aggregating the results of 28 experimental studies using driving simulators or instrumented vehicles reported that typing or reading text messages significantly slowed reaction time, increased lane deviations and increased the length of time drivers looked away from the roadway (Caird et al., 2014).

Cellphone use also affects how drivers scan and process information from the roadway. Drivers generally take their eyes off the roadway to dial or manipulate a hand-held phone. In contrast, drivers engaged in cellphone conversations and other forms of cognitive distraction tend to concentrate their gaze toward the center of the roadway (Recarte & Nunes, 2000; Recarte & Nunes, 2003; Reimer et al., 2012), but their attention still may be diverted from driving and this may make it difficult for drivers to process what they are looking at (Strayer et al., 2003).

Researchers have found that brain activity associated with visual processing and attention is suppressed when drivers are cognitively distracted (Bowyer et al., 2009: Strayer et al., 2006; Just et al., 2008). Consequently, cognitive distractions can lead to so-called “inattention blindness” in which drivers fail to comprehend or process information from objects in the roadway even when they are looking at them (Strayer et al., 2003).

States initially banned drivers from using cell phones to call or text. In 2001, New York became the first state to ban hand-held phone conversations by all drivers. Broader bans that encompass all types of electronic devices, uses beyond texting, and even simply holding these devices seem to be most promising, rather than laws that only target talking or texting. Currently, 13 states (Alabama, Arizona, Georgia, Hawaii, Indiana, Massachusetts, Michigan, Missouri, Oregon, Tennessee, Virginia, Washington and West Virginia) ban drivers from holding electronic devices.

Thirty-five states and the District of Columbia have full bans for teen drivers on all electronic device use, including hands-free use. Little is known about the effects of these laws as currently written. However, the earliest laws against cellphone use by young, novice drivers did not seem to change teens’ behavior as much as laws that apply to all drivers (Foss et al., 2009; Goodwin et al., 2012). This may be because they are harder to enforce.

Electronic device laws by state in detail

IIHS found that the earliest all-driver bans on hand-held phone conversations had large and lasting effects on phone use (Braitman & McCartt, 2010; McCartt et al., 2010).

Studies of the effects of the early hand-held phone and texting bans on crashes are less conclusive.

Early analyses by HLDI found that collision claims either didn’t change or went up with hand-held phone bans (Trempel et al., 2011) and texting bans (HLDI, 2010). IIHS later reviewed 11 studies of the effects of all-driver hand-held phone bans and texting bans on crashes, including the two HLDI studies, and found the results were mixed (McCartt et al., 2014).

A number of later studies showed that fatal crashes fell in states with bans on hand-held phone use (Flaherty et al., 2020; French & Gumus, 2018; Rocco & Sampaio, 2016; Rudisill et al., 2018). However, these studies had methodological limitations and large variation in estimated effects.

Many of the early studies of cellphone bans were conducted before smartphones became ubiquitous. The vastly increased functionality of these devices compared with earlier types of cellphones has fundamentally changed the nature of device-based distraction.

As cell phones have changed, state lawmakers have sought to address different types of device use by drivers beyond talking and texting.

IIHS evaluated the relationship between rear-end crash rates and broad laws in California, Oregon and Washington that prohibit practically all electronic device use behind the wheel. Rear-end crash rates decreased significantly in Oregon and Washington after more comprehensive bans went into effect, but this was not the case in California (Reagan et al., 2023).

The mixed results suggest that the specific wording of the laws and other factors like the severity of penalties seem to make a difference. Oregon and Washington banned any “holding” of an electronic device and specified that the bans apply to times when the vehicle is stopped temporarily. California’s law did not state whether its ban applies to times when the vehicle is stopped temporarily. Also, by prohibiting “holding and using” an electronic device, rather than simply “holding” one, it made it possible, at least theoretically, for a cited driver to argue that they were holding their phone but not using it, and therefore weren’t violating the law.

Crash avoidance technology may be the most promising avenue for reducing crash risks related to distractions of any type. Warnings can redirect a distracted, inattentive or sleepy driver’s attention back to the roadway if the potential for a collision is detected. Some systems attempt to avoid the collision altogether if a driver does not respond fast enough or does not respond at all.

A promising recent development is camera-based driver monitoring systems designed to alert the driver when they are looking away from the road for too long. Initially deployed for use with other driver assistance technology, some automakers have deployed the camera-based systems as a standalone feature to counter distraction and fatigue.

Automakers are integrating “infotainment” systems into vehicles to let drivers and other occupants plug in or wirelessly connect portable electronic devices such as cellphones to vehicle entertainment and communication systems.

On the one hand, increased complexity of the center stack area of the vehicle has been associated with increased crash risk (Dingus et al., 2016). However, designers are also leveraging technology to implement systems that require less visual-manual demand. For example, automakers, in conjunction with Google and Apple, offer Android Auto and Apple CarPlay. These two systems allow drivers to connect their phones to use the vehicle’s built-in microphone and speakers and view a simplified phone interface that is projected on the infotainment screen. Strayer et al. (2018) found lower distraction levels when completing secondary tasks with Android Auto and Google CarPlay compared with the native systems designed by five different automakers.

Many newer infotainment systems and portable devices can be controlled using voice commands. Drivers take shorter glances away from the roadway and keep their eyes on the road for a greater proportion of the time when using voice commands than when using their hands (Ranney et al., 2005; Owens et al., 2010; Owens et al., 2011; Mehler et al., 2016; Reimer et al., 2016), and this is true for older drivers as well as younger drivers (Reagan et al., 2019).

However, voice systems aren’t all the same, and the benefits can vary (Reagan & Kidd; 2013). An IIHS study found that drivers were able to place calls and enter addresses into a navigation system during highway driving more quickly and keep their eyes on the roadway longer when using a system in which a single detailed voice command was used to complete the tasks, compared with a system in which multiple voice commands were used to navigate different menus (Mehler et al., 2016). On the flip side, drivers experienced many more errors when entering an address using one long voice command than when entering it using multiple short voice commands. 

The effects of voice recognition technology on crash risk are unknown. NHTSA has issued voluntary guidelines for integrated infotainment systems in an effort to minimize the visual and manual distraction potential of these systems (Office of the Federal Register, 2012). NHTSA also has provided similar voluntary guidelines for makers of portable and aftermarket devices (Office of the Federal Register, 2016).

Phone applications that restrict or limit access to electronic devices also have been developed. These apps generally work when vehicles are in motion and can silence the phone, redirect incoming calls to voicemail or respond to text messages with a preprogrammed message.

Apple released its Do Not Disturb While Driving feature in the fall 2017. IIHS conducted a nationally representative survey of iPhone owners and found that only about 1 in 5 had the feature set to activate automatically when they drive (Reagan & Cicchino, 2020).