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.

It's not clear that banning hand-held phone use and texting reduces crashes. This is the case even though IIHS research has documented that bans on hand-held phone use reduce overall phone use. Crashes have increased in recent years, but overall cellphone use has not. Drivers are distracted by things other than cellphones, so prohibiting phone use will not eliminate distracted driving. Broader countermeasures that keep drivers from becoming distracted or that mitigate the consequences of distracted driving, such as crash avoidance technology, may be more effective than cellphone bans.

A 2018 national observational survey found that 3.2 percent of drivers stopped at intersections were talking on hand-held phones at any moment during the day (National Center for Statistics and Analysis, 2019). Combining this observational data with self-reported data on hand-held and hands-free phone use, the federal government estimates that 9.7 percent of drivers were using a handheld or hands-free cellphone during any moment of the day.

National observation surveys indicate the rate of drivers texting at any moment during the day has risen since 2009, especially among younger drivers. In 2018, 2.1 percent of all drivers and 4.2 percent of drivers estimated to be 16-24 years old were observed texting or otherwise manipulating hand-held devices (National Center for Statistics and Analysis, 2019). That's a substantial increase from 2009, when 0.6 percent of all drivers and 1.1 percent of drivers 16-24 years old were observed manipulating phones. 

Observational surveys conducted by IIHS in 2014 and 2018 in Virginia found an increase in cellphone manipulation from 2.3 percent of drivers to 3.4 percent (Kidd & Chaudary, 2019).

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 2017, 3,166 people died in motor vehicle crashes in which distraction was deemed a contributing factor. That is about 9 percent of all crash deaths. Of that number, 434, or 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, another analysis of the same data found that talking on a hand-held cellphone did not significantly increase crash risk (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 three analyses of data 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).

Bans on hand-held phone conversations while driving are widespread in other countries and are becoming more common in the U.S. In 2001, New York became the first state to ban hand-held phone conversations by all drivers. Now 21 states and the District of Columbia have similar laws.

Texting is banned for all drivers in 48 states and the District of Columbia.

Thirty-eight states and the District of Columbia restrict cellphone use by young drivers.

Cellphone use laws by state in detail

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

Phone bans specifically targeting young drivers seem to have less effect (Foss et al., 2009; Goodwin et al., 2012).

There is scant information on drivers' compliance with texting bans. A 2009 IIHS survey of drivers found that among 18-24 year-olds, 45 percent reported texting while driving in states that bar the practice, just shy of the 48 percent of drivers who reported texting in states without bans (Braitman & McCartt, 2010). Among drivers ages 25-29, 40 percent reported texting in states with bans, compared with 55 percent in states without bans.

The National Highway Traffic Safety Administration has conducted high-visibility enforcement campaigns in Hartford, Conn., Syracuse, N.Y., the Sacramento Valley Region in California, and in the state of Delaware as a way to increase compliance with cellphone and texting bans. After programs of publicized, high-intensity enforcement of hand-held cellphone and texting bans were implemented, the number of drivers observed holding a phone to their ear declined (Cosgrove et al., 2011; Schick et al., 2014). Observed manipulation of hand-held phones (e.g., dialing, texting) decreased significantly in Syracuse, N.Y., and Hartford, Conn., following the enforcement initiative and did not decrease in the comparison communities.

It's not clear whether banning hand-held phone use or texting reduces crashes. A 2009 analysis by the Highway Loss Data Institute (HLDI) found that hand-held bans had no effect on insurance collision claim rates (Trempel et al., 2011). Researchers compared rates of claims for crash damage in three states and the District of Columbia before and after hand-held phone use bans went into effect and found no significant change in claim rates for two jurisdictions relative to comparison states and small, but significant, increases in claim rates in the other two.

A 2010 HLDI study examined rates of insurance collision claims before and after driver texting bans were enacted in four states (HLDI, 2010). There was no significant change in one state relative to comparison states and significant increases of 7-9 percent in three states. Increases in claim rates also were found for drivers 25 and younger in these three states.

IIHS reviewed 11 studies of the effects of all-driver hand-held phone bans and texting bans on crashes, including the two HLDI studies (McCartt et al., 2014). The results were mixed, so it's not clear if laws limiting drivers' cellphone use are having beneficial effects on crashes.

Bans may not have a beneficial effect on crashes even with strong enforcement. An analysis comparing insurance collision claims in counties with high-visibility enforcement of phone and texting bans and counties without it didn't find a corresponding reduction in crashes reported to insurers (HLDI, 2013).

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 it detects the potential for a collision. Some systems attempt to avoid the collision altogether if a driver does not respond fast enough or does not respond at all.

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.

Many newer infotainment systems and portable devices can be controlled using voice commands. Several experimental studies have shown that drivers take shorter glances away from the roadway and keep their eyes on the road for a greater proportion of the time when interacting with a portable device 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 experience 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, 2018).