Distraction: Why is Mobile Phone Use while Driving a Problem?

Types of Distraction

Every year nearly 1.3 million people die and 50 million worldwide are injured as a result of road traffic crashes.  Road traffic accidents are the leading cause of death among young people aged 15 – 29. National studies have attributed on average between 9 and 16 percent of annual crashes to driver distraction. 


Driving is a complex task that involves sensory (looking where you are going, listening to traffic sounds), physical (turning the steering wheel, pressing the breaks) and cognitive resources (planning a route, deciding when to change lanes). Performing a secondary task – eating, listening to the radio, making a phone call – makes additional demands thus creating an overload that can distract from the primary task: driving. 


Distraction illustrationThree main types of distraction for drivers have been identified:

  • Visual: taking your eyes off the road
  • Manual: taking your hands off the wheel
  • Cognitive: taking your mind off of driving



Some of these types of distraction are more obvious than others – we can only look at one place at a time; if you are looking at a phone, you are not looking at the road. Similarly, if you are reaching for an object in the car, you do not have full manual control over the wheel. Cognitive demands are more complicated. We often think that we can easily perform many tasks simultaneously. Research shows that this is not the case. Depending on how complicated or demanding a task is, adding a second task may impair your performance of the first task. This is similar to if you try to open a large number of programs at once on a computer – at some point, the computer will probably slow down or even temporarily pause work to deal with the number of demands. Similarly, when cognitive demands are too great, the brain struggles to cope.


An experienced driver travelling on a known route can usually drive fairly automatically, and little direct attention is needed to stay on route and respond to traffic signals. Complex traffic situations, however, may demand greater cognitive function – greater attention – to complete. For example turning left across incoming traffic (e.g. at an intersection without a traffic light), or changing lanes in heavy traffic.  At these times, the cognitive function (concentration) needed to perform this task is high. Performing a secondary task – such as responding to a phone call – is likely to cause the driver to make mistakes that may result in a car accident. 


Currently, there is uncertainty in the literature regarding which type of distraction is most harmful to driving. The majority of studies performed (as of January 2014), suggest that cognitive distractions are the most detrimental to driving. These studies are predominantly experimental and epidemiological crash studies. A few recent studies using naturalistic methodology and measuring both crashes and near crashes suggest that visual or manual distractions may be more harmful to driving than cognitive distractions (naturalistic methodology in this instance refers to studies of drivers in natural on-road settings, usually through the use of cameras and sensors mounted on the driver's car).

  Woman looking at phone and driving


Mobile Phone Use and Distracted Driving

Car crash after distracted drivingThe impact of using a mobile phone on the risk of being involved in a car accident is difficult to ascertain, but studies suggest that drivers using a mobile phone are approximately four to six times more likely to be involved in a car accident. This increased risk appears to be similar for both hand-held and hands-free phones, though research on this issue is still inconclusive. Text messaging has been found to increase the risk by as much as 23 times. 


Tasks associated with mobile phone use involve one or more types of distraction: for example, dialing a phone number or writing a text message would involve visual, manual and cognitive  distraction; talking on a hands-free device uses cognitive and auditory functions, and reaching for a phone visual and manual  distraction. These distractions are a problem because they divert our limited attention away from driving towards a secondary (non-driving) task. 


Studies have shown that use of a mobile phone while driving results in distraction that can impair driving performance in a number of ways, such as longer reaction times (e.g. braking reaction time, reaction to traffic lights, reaction to potential  immediate hazards), impaired ability to keep in the correct lane, riskier decision making, and an overall reduction in awareness of the driving situation . The effects are comparable, or even more severe than driving under the influence of alcohol (e.g. one study compared talking on a mobile phone to having a blood alcohol level of 80mg/100ml - the legal limit in the U.K. – and found that driving behavior was more impaired by the phone conversation. It should be noted that talking on the phone is transient, whereas intoxication is longer lasting).


The effects are greater for talking on a phone than for talking with a passenger. This is probably because passengers are aware of additional demands on your attention that arise while driving – your need to concentrate while making a turn, or navigating traffic – and will pause the conversation. A person on the other end of a phone call is not aware of these demands, and will continue the conversation during periods when driving demands your full attention. 


For new drivers, for whom driving is not automatic, studies have found that cell phone use and other secondary tasks have greater impact on driving ability than for experienced drivers. For this reason, some countries have stricter rules for young and/or provisional drivers. For example, several Australian states have stricter limits on speed, alcohol consumption, the number of passengers allowed in the car, and use of mobile phones for provisional drivers than for more experienced drivers.

A game developed by the U.K. government as part of the "Think" road safety campaign demonstrates the effects of driving while speaking on the phone.


World Health Organization (2011) "Mobile Phone Use: A Growing Problem of Driver Distraction"; it is difficult to estimate with any certainty the rate at which distraction contributes to car accidents as data on distraction is not systematically recorded, and drivers have an invested interest in not reporting possible sources of distraction due to possible legal implications of such admissions.


According to DaCoTa 2013 "Driver Distraction" report, a product of the European Commission, different study types have produced different risk estimations. "Case-crossover car accident studies have demonstrated that using a mobile phone while driving increases the risk by a factor of 4 (Redelmeier & Tibshirani; McEvoy et al., 2005). Case-control car accident studies (Violanti & Marshall, 1996; Laberge-Nadeau et al., 2003) also recorded a higher risk for mobile phone users (factors 5.6, 1.1/1.2 males/females). However, three naturalistic driving studies show no increased risk with mobile phone use (Klauer et al., 2006; Olsen et al., 2009; Hickman et al., 2010)." The authors attribute part of this difference to a difference in how tasks are defined: the car accident studies tend to look at mobile phone use as a whole, whereas naturalistic studies divided this task into parts: dialing a number, reaching for the phone, talking etc. Another reason is that naturalistic studies substitute car accidents with "near-car accidents" due to small sample sizes, which may reduce estimations. A recent naturalistic study (Klauer et al. 2014) found that tasks that involved the driver looking away from the road, such as reaching for a phone, dialing, and text messaging, significantly increased the risk of car accidents and near- car accidents. A significant increase was not found for tasks that did not directly involve a visual component (such as talking on the phone).


The above sources appear to agree on this point, though Klauer et al. 2014 divide distraction by task: reaching for the phone is a high risk task, which is presumably eliminated for mounted hands-free devices. Dialing is equally high risk, and exists for both hands-free and hand-held phones.