Fact sheet

Use of the mobile phone while driving

Summary

Using a mobile phone while driving has negative effects on driving behaviour. This is the case for conducting a conversation, dialling a number, and sending text messages as well as for using the extra functions that smartphones offer, like accessing internet or social networking sites. An elaborate American study indicates that making a phonecall with a handheld phone doubles the risk of a crash. Reading and typing text messages (texting) makes the risk of a crash six times higher. The negative effects of mobile phone use are not only due to physical, visual and auditory distraction caused by operating the phone and the vehicle at the same time, but also because drivers have to divide their attention between using the phone and driving (cognitive distraction). As cognitive distraction also poses a danger, hands-free phone use is not notably safer than hand-held use. However, a total prohibition of mobile phone use by drivers is not realistic. For this reason, only hand-held use is forbidden in many countries. Besides legislation, technical measures, information and education can enhance responsible use of the mobile phone.

Background and content

The rapid growth of the possession and use of mobile phones in recent years, has generated a wide interest in safety issues like distraction while driving (see also the archived SWOV Fact sheet Attention problems behind the wheel). The fact that many drivers own and use a mobile phone has raised concerns among scientists, the media, and policymakers. The early mobile phones had only a call function, but the modern smartphones have more and more functions, e.g. text messaging, e-mail, internet use, that may distract the driver.

This fact sheet describes the reasons why it is hazardous to use a phone in the car, discusses the effect on the crash risk, and discusses the possible measures and the effectiveness of legal prohibition. This fact sheet will only look into the use of mobile phones by drivers. Information about the use of mobile phones by cyclists and pedestrians and its consequences can be found in the SWOV fact sheet Phone use by cyclists and pedestrians.

Facts

In which ways can a mobile phone distract the driver?

Mobile phone use can distract drivers in various ways:

  1. visually, such as by looking at a screen instead of at the road;
  2. auditory distraction, when focusing on sounds like, for instance, a ringtone, so that fewer environmental sounds can reach the road user;
  3. bio-mechanically/physically, such as when a mobile phone is operated manually;
  4. cognitively, when the driver is thinking about something (about the conversation he/she is conducting, for instance) not related to the driving task. 

As the examples show, the use of a mobile phone while driving involves all these types of distraction. Cognitive and auditory distraction mainly occur during the actual conversation. Text messaging and accessing the internet or e-mail cause cognitive, physical and visual distraction.

Which effects does the use of mobile phones have on performing the driving task?

Various (review) studies have investigated the behavioural effect of the use of a mobile phone while driving (Basacik, Reed & Robbins, 2011; Collet, Guillot & Petit, 2010a; 2010b; Stelling-Konczak & Hagenzieker, 2012). These studies indicate the following negative effects.

Slower reactions

Several driving simulator studies and meta-analyses of mainly driving simulator studies  and laboratory studies indicate that a telephone conversation causes considerably slower reactions of the driver to the traffic environment. Based on simulator studies, laboratory studies, and field experiments carried out on an exercise track, the increase in reaction times while phoning is estimated to be 20-40%. While phoning, drivers have a longer braking reaction time in reaction to changes in speed of the vehicle ahead of them or in reaction to road signs. They eventually brake harder: they come to a standstill more quickly. The distance to a vehicle ahead, a stop line or a junction turns out to be shorter at standstill. Reaction times also increase while text messaging and when messages are sent or received via a social network site. In a driving simulator study by Basacik, Reed & Robbins (2011) the latter led to a 30% increase in reaction time. 

Less control

Drivers appear to have less control over the vehicle while using the mobile phone. Keeping in lane turns out to be more difficult. This is the case for conducting a conversation, dialling a number, text messaging, and sending and receiving messages via a social network site. Furthermore, merging and turning left are negatively affected by the mobile phone use (Cooper et al., 2003). While phoning, drivers also adjust less well to possible hazardous road conditions, such as a slippery road surface (Cooper et al., 2003). In a driving simulator, conducting a phone conversation was also found to lead to an increase in crashes.

Less attention for relevant visual information

During mobile phone use, drivers fail to take notice of all kinds of relevant information. Drivers are for instance more likely to miss changes in the road environment when they are using a mobile phone than when the phone is not being used. This is often the result of looking at the road for shorter time spans, for example while text messaging or using a social network site. But also when drivers do have their eyes focused on the road, for instance while conducting a phone conversation, they can fail to notice all kinds of things because their mind is elsewhere. They look in the right direction, but do not consciously see an important object. This phenomenon is known as ‘inattentional blindness’. The phone conversation can also result in narrowing of the field of vision, as one tends to look straight ahead and less at objects on the periphery of the field of vision. For example, the rear and side mirrors and odometers are consulted less frequently.

Increased mental effort

Mobile phone use requires greater mental efforts. As a result one pays less attention to other things. When drivers are using the mobile phone, their so-called situation awareness, consisting of the elements of perception, understanding and prediction, deteriorates in all three aspects, because the telephone conversation demands the attention (Parkes & Hooijmeijer, 2000). The extent to which the mental load increases (and driving performance deteriorates) is dependent on the intensity of the conversation and the demands set by the driving task at that particular moment.

Do drivers adjust their behaviour?

Drivers can adjust their behaviour in different ways. On a strategic level, drivers can take decisions about the use of the phone itself. Subsequently, drivers can adjust their driving behaviour if they use the phone.

Even though most drivers realize that mobile phone use renders the driving task more difficult, they nevertheless tend to use the phone when they consider the conversation to be important. The extent to which drivers adjust their phone use is partly dependent on the driver’s age. Young drivers, who generally think that they can sufficiently compensate for distraction during the driving task and who often overestimate their driving performance, use the phone more frequently while driving (Schlehofer et al., 2010). The inability of drivers to estimate to what extent this actually affects their driving task makes it difficult for drivers to adjust their phone use (Horrey, Lesch & Garabet, 2008).

Drivers often adjust their driving behaviour while using the phone in order to be able to perform this extra task: this is known as compensatory behaviour. The most obvious example of compensatory behaviour is lower speed and (sometimes) greater variation in speed. Drivers also tend to drive at greater headway distances.

Is hands-free phoning safer than hand-held phoning?

Hand-held versus hands-free phoning is and remains one of the most frequently studied issues. An ample majority of the studies conclude that hands-free phoning has no significant advantage compared to hand-held phoning. Although in the case of hand-held phoning only one hand is available for the driving task, the most negative characteristic of mobile phones equally applies for hands-free phoning - namely shifting the focus of attention from the driving task to the conversation. The negative effects on the driving task, such as the increased reaction times, are similar for hand-held and hands-free phoning (Caird et al., 2008).

Is there a difference between talking on the phone and talking to passengers?

One of the predominant arguments against banning mobile phone conversations while driving is that conversing with a passenger is allowed. Indeed, the contents of the two types of conversation seem to be hardly different. However, the major difference is that a conversation with a passenger is self-regulating as a result of direct contact. The passenger is aware of the driving situation, so that the complexity and the pace of the conversation is often adjusted (Drews, Pasupathi & Strayer, 2008); this as opposed to talking to a person on the phone. Another difference seems to be the sound quality: in mobile phones this may not be optimal. Therefore, more attention and effort are required to understand the message, and this may be at the expense of the driving performance. These differences between a phone conversation and a passenger conversation are not always found in studies comparing the behavioural effects of the two types of conversation (Stelling-Konczak & Hagenzieker, 2012). Whereas some of these studies find that talking on a mobile phone results in a worse performance than talking to a passenger, other studies indicate that both types of conversation have the same effect on the driving task.

How and how often do car drivers use a mobile phone?

In a study conducted in 2010 among 405 drivers in possession of a mobile phone or other electronic equipment in their car, 22% of the drivers reported making a handheld phone call in their cars at least once a week and 40% reported making handsfree calls while driving (Netherlands Government Information Service (RVD)). Data from a large-scale written survey held among more than 100,000 respondents in 2009 indicates similar results (Biervliet et al., 2010). No Dutch figures are available about the use of the phone while driving for purposes other than making a telephone call, such as text messaging or searching for information. Recent international surveys indicate that 25-35% of the drivers read text messages and 14-30% send text messages (Lansdown, 2009; Young & Lenné, 2010).

What is the risk of using a mobile phone in the car?

Although mobile phone use (handheld as well as handsfree) often leads to worsening of the driving performance, it is not easy to indicate to what extent it impacts the risk of being involved in a crash. Crash studies indicate an increased crash rate. Two, now classic studies found that the risk of mobile phone use is approximately a factor of 4 higher than if one does not make a call (McEvoy et al., 2005; Redelmeier & Tibshirani,1997). Other crash studies show that mobile phone users have a factor of 1.1 to 5.6 higher risk of having a car crash than non-users (Laberge-Nadeau et al., 2003; Violanti & Marshall, 1996).

Remarkably, the first Naturalistic Driving or ND studies[1] do not indicate an increase in risk due to mobile phone use as far as conducting a conversation is concerned (see for example Klauer et al., 2006; Olson et al., 2009). Both the conventional method which, based on data from telephone companies, examined whether the phone was in use at the time of the crash and the first ND-studies were criticized (e.g. Young, 2012). In the conventional studies it was found to be impossible for the police to accurately determine the time of the crash. A major point of criticism about the first ND-studies was that the risks were calculated on the basis of near-crashes and not on actual crashes.

Recently a very large ND-study has been carried out in America in which the sample was large enough to calculate the risks of mobile phone use based on real crashes (Dingus et al., 2016). For 905 crashes this study recorded on film what the driver was doing immediately before the crash. We must consider that this American research can give only an indication of the risks in the Netherlands. We do not know, for instance, whether the use of the mobile phone is the same and driving in America also differs from driving in the Netherlands. For example, a Dutch driver encounters many cyclists. Furthermore, young drivers and older drivers (65 and older) were somewhat over-represented in the sample.

Table 1 shows the risks and prevalences of some of the distracting activities that were considered in the study by Dingus et al. (2016). The activity can be found in the column on the left.

The relative risk of a distracting activity while driving (in comparison to driving without distraction) cannot be calculated exactly. However, for large sample sizes, such as in this study, the relative risk can be calculated as a so-called 'odds ratio' (see for the difference between the two concepts: Houwing, 2013). In the middle column of Table 1, these odds ratios are presented. Interpreted as a relative risk, an odds ratio of 2.2 for ‘conducting a telephone conversation’ indicates that the risk of a crash is 2.2 times higher than for no conversation being conducted by (handheld) phone. Behind the odds ratio two numbers are given in parentheses. These show the 95% confidence interval. The odds ratio is an estimate. The best estimate of the relative risk of conducting a telephone conversation is 2.2, but it is at least 95% certain that the odds ratio is greater than 1.6 (the first number in parentheses) and smaller than 3.1 (the second number).

The right-hand column shows the prevalence of the activity. Conducting a telephone conversation has a prevalence of 3.24%. This means that 3,24% is the average proportion of time drivers conduct a conversation by handheld phone.

Table 1. De odds ratios (‘relative risks’) and prevalences of some of the distracting activities of drivers (Dingus et al., 2016).

 

[1] Naturalistic Driving or ND studies measure the actual – ‘naturalistic’– behaviour of drivers in traffic. More information about this method can be found in the archived SWOV Fact sheet Naturalistic Driving: observing everyday driving behaviour.

What is the risk caused by the extra features of the mobile phone while driving?

Initially, research into the effect of mobile phone use on driving behaviour was restricted to hand-held/hands-free phoning. Meanwhile, the use of the phone for text messaging has increasingly become the subject of research, especially in the United States and Australia. Recent ND studies among truck drivers indicate that sending text messages strongly increases the risk of a crash by a factor of more than 23 or even as high as 160 (Hickman, Hanowski &Bocanegra, 2010; Olson et al.,2009). The crash risk among drivers of passenger cars due to sending text messages is unknown, but is expected to be high as well. While sending a text message both the driver’s eyes and mind are occupied for a considerable length of time with other things than they should be occupied with, i.e. the driving task. This is also the case for a number of functions of a smartphone, like accessing e-mail, internet, and social media. Of late, the road safety effects of being engaged in these activities while driving has been gaining more and more attention. As yet, no specific risk data are known, but considering the similarity of some of the smartphone functions with sending and receiving text messages on an ordinary mobile phone, the crash risk related to these functions is expected to also be high.

How effective is a legal prohibition?

One of the most frequently applied legal measures against phone use in a vehicle is the banning hand-held phone use. In the Netherlands, this prohibition has been in force since April 2002. In a number of countries, hands-free use of the mobile phone is also prohibited. However, the effect of legislation on driving behaviour turns out to be disappointing, especially in the case of young people (see for instance Foss et al., 2009). In the Netherlands, no objective data is available about the use of the mobile phone since the introduction of the legal prohibition. More subjective data, about self-reported use (Biervliet et al., 2010; see Table 2), shows that the use of hand-held phones in the car has been increasing, rather than decreasing the last few years: in 2003, the first year following the introduction of the legal prohibition, 77% of respondents stated that they never used a hand-held phone in the car; in 2005 this was 75% and in 2009 71%. Compared with the situation prior to the legal prohibition, however, there has been an improvement: in 2001, 60% of respondents stated that they never used a hand-held phone. Hands-free phoning has also increased, rather than decreased: in 2003, 63% of respondents stated they never phoned hands-free; in 2005 this was 59% and in 2009 53%. The legal prohibition of hand-held phoning seems to have had an effect on hands-free phoning as well: namely in 2001, 42% stated never to phone hands-free. In 2003 this was 63%.

Table 2. Percentage of people in the Netherlands indicating that they often, sometimes or never use a hand-held or hands-free phone while driving (Biervliet et al., 2010).

 

In the Netherlands, the number of fines for hand-held mobile phoning has sharply increased over the years: from 55,000 in 2003 to 140,000 in 2010 (figures from the Central Fine Collection Agency (CJIB). Obviously, these figures not only refer to the number of offences, but are also dependent on the level of enforcement.   

A positive public opinion is important for the success of a legal measure. Various studies show that a general ‘feeling’ prevails that it is hazardous to use a hand-held mobile phone while driving and that it is necessary to restrict this. However, in general, the idea is that hands-free use of mobile phones in traffic is non-hazardous (Netherlands Government Information Service (RVD), 2010).

Which other measures can be taken in addition to legislation?

In addition to the legislator, telephone manufacturers also play a part in improving road safety. In order to reduce the risk of using a phone while driving, they can take human characteristics into account when designing new mobile phones. For instance, voice-activated devices have been developed that are expected to interfere less with the driving task compared with manually operated devices; research has, however, found that voice-activated systems on the smartphone also cause distraction (Strayer et al., 2015). It is also possible to develop technical provisions that make it impossible to use a phone while driving. An example is the ‘Auto Reply App’ introduced by the Dutch Traffic Safety Association. This app prevents the phone from ringing at speeds higher than 10 km/h. At the same time a message is sent to the person who is calling which says that the driver is presently not available as he or she is behind the wheel.

During the driver training attention should be paid to the problem of distraction and, subsequently, to the use of a mobile phone while driving. Furthermore, public information campaigns can be conducted.  In the Netherlands a campaign to increase awareness and enforcement of distraction was conducted in 2010 and 2011 to inform road users about the risks of, among others, making phone calls and sending text messages while driving. The campaign also focuses on alternative behaviour: if you need to make an urgent phone call, do so handsfree and be brief; do you want to send a text message, tweet, or use the internet, first stop the car in a safe spot.

Conclusion

Based on the results of behavioural studies, we conclude that the use of a mobile phone has a negative effect on driving behaviour. This is caused by cognitive distraction, whether or not in combination with visual, auditory and physical distraction. Although physical distraction can be reduced or diminished by various appliances (for instance, hands-free devices and voice activation), cognitive distraction remains an important problem for drivers who use their phone while driving. Having a hands-free conversation on a mobile phone has therefore no significant safety advantages compared with a hand-held conversation. Using the extra functions of a mobile phone, like sending text messages, is also quite hazardous, because during the use of such functions the driver’s eyes and mind are off the road for longer periods of time. Sending text messages increases the risk of crashes considerably and the same is probably the case for using the new functions of smartphones, like e-mail, internet or social network sites.

Education and information campaigns can contribute to making the public more aware of the risks of the use of a mobile phone in traffic. However, research has shown that people who are aware of the risks do not always adjust their behaviour accordingly; this applies to young road users in particular. The contribution of education and information to reducing the use of a mobile phone while driving may therefore be limited.

Publications and sources

Basacik, D., Reed, N. & Robbins, R. (2011). Smartphone use while driving: A simulator study. PPR592. TRL, Wokingham.

Biervliet, N., Zandvliet, R., Schalkwijk, M. & Gier, M. de (2010). PROV 2009: Periodiek Regionaal Onderzoek Verkeersveiligheid. Dienst Verkeer en Scheepvaart, Delft.

Caird, J.K., Willness, C.R., Steel, P. & Scialfa, C. (2008). A meta-analysis of the effects of cell phones on driver performance. In: Accident Analysis & Prevention, vol. 40, nr. 4, p. 1282-1293.

Collet, C., Guillot, A. & Petit, C. (2010a). Phoning while driving I: A review of epidemiological, psychological, behavioural and physiological studies. In: Ergonomics, vol. 53, nr. 5, p. 589-601.

Collet, C., Guillot, A. & Petit, C. (2010b). Phoning while driving II: A review of driving conditions influence. In: Ergonomics, vol. 53, nr. 5, p. 602-616.

Cooper, P.J., Zheng, Y., Richard, C., Vavrik, J., et al. (2003). The impact of hands-free message reception/response on driving task performance. In: Accident Analysis and Prevention, vol. 35, nr. 1, p. 23-35.

Dingus, T.A., Guo, F., Lee, S., Antin, J.F., et al. (2016). Driver crash risk factors and prevalence evaluation using naturalistic driving data. In: Proceedings of the National Academy of Sciences of the United States of America PNAS. doi:10.1073/pnas.1513271113.

Drews, F.A., Pasupathi, M. & Strayer, D.L. (2008). Passenger and cell phone conversations in simulated driving. In: Journal of Experimental Psychology: Applied, vol. 14, nr. 4, p. 392-400.

Foss, R.D., Goodwin, A.H., McCartt, A.T. & Hellinga, L.A. (2009). Short-term effects of a teenage driver cell phone restriction. In: Accident Analysis & Prevention, vol. 41, nr. 3, p. 419-424.

Hickman, J.S., Hanowski, R.J. & Bocanegra, J. (2010). Distraction in commercial trucks and buses: assessing prevalence and risk in conjunction with crashes and near-crashes. Federal Motor Carrier Safety Administration, Washington D.C.

Horrey, W.J., Lesch, M.F. & Garabet, A. (2008). Assessing the awareness of performance decrements in distracted drivers. In: Accident Analysis & Prevention, vol. 40, nr. 2, p. 675-682.

Houwing, S. (2013). Estimating the risk of driving under the influence of psychoactive substances. SWOV, Leidschendam.

Klauer, S.G., Dingus, T.A., Neale, V.L., Sudweeks, J., et al. (2006). The impact of driver inattention on near-crash/crash risk: An analysis using the 100-Car Naturalistic Driving Study data. Virginia Tech Transportation Institute, Blacksburg, Virginia.

Laberge-Nadeau, C., Maag, U., Bellavance, F., Lapierre, S.D., et al. (2003). Wireless telephones and the risk of road crashes. In: Accident Analysis and Prevention, vol. 35, p. 649-660.

Lansdown, T. (2009). Frequency and severity of in-vehicle distractions: a self-report survey. Paper gepresenteerd op Driver Distraction and Inattention Conference 2009, Gothenburg, Sweden.

McEvoy, S.P., Stevenson, M.R., McCartt, A.T., Woodward, M., et al. (2005). Role of mobile phones in motor vehicle crashes resulting in hospital attendance: a case-crossover study. In: British Medical Journal, vol. 331, p. 428-431.

Olson, R.L., Hanowski, R.J., Hickman, J.S. & Bocanegra, J. (2009). Driver distraction in commercial vehicle operations. US Department of Transportation, Washington, DC.

Parkes, A. & Hooijmeijer, V. (2000). The influence of the use of mobile phones on driver situation awareness. Transport Research Laboratory, Crowthorne, England.

Redelmeier, D.A. & Tibshirani, R.J. (1997). Association between cellular-telephone calls and motor vehicle collisions. In: The New England Journal of Medicine, vol. 336, p. 453-458.

Rijksvoorlichtingsdienst (2010). Campagne ‘Afleiding in het Verkeer & Rij Voorbereid (L41). Eindrapportage campagne-effectonderzoek. Rijksvoorlichtingsdienst Ministerie van Algemene Zaken, Den Haag.

Schlehofer, M.M., Thompson, S.C., Ting, S., Ostermann, S., et al. (2010). Psychological predictors of college students' cell phone use while driving. In: Accident Analysis and Prevention, vol. 42, nr. 4, p. 1107-1112.

Stelling-Konczak, A. & Hagenzieker, M. (2012). Afleiding in het verkeer; Een overzicht van de literatuur. R-2012-4. SWOV, Leidschendam.

Strayer, D.L., Cooper, J.M., Turrill, J., Coleman, J.R. & Hopman, R.J. (2015). The smartphone and the driver's cognitive workload: A comparison of Apple, Google, and Microsoft's intelligent personal assistants. AAA Foundation for Traffic Safety, Washington, D.C.

Violanti, J.M. & Marshall, J.R. (1996). Cellular phones and traffic accidents: an epidemiological approach. In: Accident Analysis & Prevention vol. 28, p. 265-270.

Young, K.L. & Lenné, M.G. (2010). Driver engagement in distracting activities and the strategies used to minimise risk. In: Safety Science, vol. 48, nr. 3, p. 326-332.

Young, R.A. (2012). Cell phone use and crash risk: Evidence for positive bias. In: Epidemiology, vol. 23, nr. 1, p. 116-118.

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Updated

27 Jun 2017