Fact sheet

Distraction in traffic

Summary

Many drivers, as well as cyclists and pedestrians, are occupied with all kinds of activities that can distract their attention from traffic, like listening to music, conducting a conversation on their mobile phone, or reading and typing text messages (texting). Distraction has negative effects on traffic behaviour. The precise number of road crashes in which distraction plays a role is unknown. An extensive American study indicates that in 68% of the crashes the driver was distracted immediately before the crash. Types of distractions that were found to occur frequently, were, among others, talking to a passenger, telephone use and operating devices. Considering the increasing diffusion of electronic devices in traffic, portable media devices as well as advanced driver support systems, the number of distraction-related crashes is likely to increase. Various countermeasures can mitigate the negative effects of distraction in traffic, e.g. public information, education, or technical facilities that, for example, make it impossible to operate navigation equipment while driving, or to use a mobile phone in traffic.

Background and content

In recent decades, there has been increasing interest in the role of distraction in traffic crashes. Distraction is not a new traffic safety problem. The concern regarding distraction, however, has only begun to increase considerably when it became possible to use a mobile phone while participating in traffic (see SWOV Fact sheet Use of the mobile phone while driving). The mobile phone is still considered to be the ultimate source of distraction, but there are many more sources. Road users can, for instance, be distracted by eating and drinking, listening to music, or by looking at advertising billboards (see the archived SWOV Fact sheet Distraction caused by roadside advertising and information for more information about the latter). In recent years, the sources of distraction have increased continuously. Mobile phones have become smartphones that cannot only be used for phone calls and texting, but also for e-mail, whatsapp, surfing the internet and twitter. For some drivers the car has become an office on wheels. In addition, navigation systems, introduced not long ago  to assist the driver in his driving task, can also distract the driver. Distraction does not only affect drivers, but also other road users like cyclists and pedestrians (see also SWOV Fact sheet Phone use by cyclists and pedestrians).

The present fact sheet is the umbrella fact sheet of the three fact sheets mentioned above and is indirectly related to SWOV Fact sheet Attention problems behind the wheel (archived). The latter fact sheet takes a closer look at the consequences of ‘having your thoughts elsewhere’ when you are not occupied with other things. The present fact sheet on distraction is largely based on the SWOV report Distraction in traffic (Afleiding in het verkeer; Stelling & Hagenzieker, 2012).

Facts

What is distraction?

Road users must continuously make decisions based on how they think a traffic situation will develop and what other road users will do. A traffic situation can become life-threatening in a matter of seconds. Road users must therefore focus their attention on traffic continuously, also when the traffic task appears to be simple and they act more or less on ‘autopilot’. All the same, when on the road people are often inclined to do things that are not related to the traffic task, like conducting a telephone conversation. Performing an extra task may require so much attention that the driving performance declines and hazardous situations occur. In that case the term distraction is used.

Many definitions of distraction can be found in literature (Regan et al., 2008). One of the most widely accepted definitions is the one given by Lee et al. (2008): ‘Driver distraction is a diversion of attention away from activities critical for safe driving toward a competing activity’. Distraction is therefore diversion of the attention and not inattenion (reduced attention). Inattention occurs in the case of fatigue or when the driving task is very monotonous, like in the case of ‘polder blindness’ (see the SWOV Fact sheets Attention problems behind the wheel (archived) and Fatigue in traffic, causes and effects. When distracted, therefore, one stays alert, the attention, however, is too much focused on something other than the driving task. The definition only refers to the (car) driving task, but what applies to the driving task, is also valid for the traffic task of other types of road users.

The attention can be diverted when one begins to think of other things (daydreaming), when one starts to do things that are not related to traffic (e.g. mobile phone conversation), or when one is occupied with things that are indeed relevant for the driving task, but at that particular moment are not critical for safe road use (e.g. entering a destination into the navigating system). Not only voluntary actions can distract the road user, the road user’s attention can also be captured involuntarily by a source of distraction, for example by an advertising billboard, a striking character on the pavement, an event or an occurrence like a plane flying low. The source of distraction can be inside the vehicle (e.g. a crying child in the rear seat) or outside the vehicle (e.g. a crash on the motorway involving traffic in the reverse direction). Sounds can also distract road users.

The definition by Lee et al. (2008) may be used a lot, but does also leave much open. For example, this definition does not answer the question how much attention is required for safe performance of the driving task, nor does it specify which actions are critical at a specific moment and which actions are not.

Which types of distraction can be distinguished?

There are different types of distraction (Ranney et al., 2000):

  • visual distraction, for example when a road user has his eyes on the screen of his smartphone instead of on the road;
  • auditory distraction, for example when a cyclist listens to music through a headphone or earphones and as a result cannot hear traffic coming up from behind;
  • physical (biomechanical) distraction, for example when a road user enters a phone number manually;
  • cognitive distraction, for example when a road user is daydreaming or has his thoughts on a mobile phone conversation and not on the traffic.

Often different types of distraction occur simultaneously. For example texting while driving involves  visual, physical as well as cognitive distraction.

How often are road users distracted?

How often certain behaviour occurs is called the ‘prevalence' of that behaviour. Research indicates that the prevalence of distracting activities is considerable: a large proportion of the road users, drivers as well as cyclists and pedestrians, engage in activities that can distract them. This has been investigated with surveys and with Naturalistic Driving observations, in which the driver’s behaviour in traffic is recorded (see also the archived SWOV Fact sheet Naturalistic Driving: observing everyday driving behaviour). Dutch data on distraction is limited; therefore this fact sheet frequently uses international data.

International studies indicate that drivers spend about 30 to 50% of their driving time on distracting activities. The most important of these activities is talking with passengers. Drivers spend approximately 15 to 25%  of the time behind the wheel on conversation with a passenger (Dingus et al., 2016; Stutts et al., 2005). Furthermore, road users often listen to music (Stutts et al., 2003; Young & Lenné, 2010) and many drivers (48-65%) frequently operate devices for playing music. Cyclists also listen to music frequently: an internet survey (Goldenbeld et al., 2010) has indicated that 39% of the Dutch cyclists sometimes listen to music; 15% listen to music almost every bicycle trip they make. Another distracting activity many drivers engage in is eating and drinking.

The mobile phone is used frequently in traffic: in 2010, 22% of the Dutch drivers reported making a handheld phone call at least once a week, and 40% indicated making a handsfree phone call while driving at least once a week (Rijksvoorlichtingsdienst, 2010). More than half of the cyclists (55%) in the Netherlands were found to occasionally make a phone call while cycling (Goldenbeld et al., 2010). In recent years, more has become known about texting while driving and cycling. The most recent international surveys indicate that 25-35% of the drivers frequently read a message and between 14-30% frequently send a text message. The internet survey by Goldenbeld et al. (2010) indicates that 35% of the cyclists in the Netherlands sometimes send a message and 49% sometimes read a message while cycling. 

Research indicates that young road users engage in all sorts of distracting activities as much as older road drivers do, but that the activities are different. Young drivers, for example, use modern devices like smartphones or music players more frequently (see for example Goldenbeld et al., 2012; McEvoy et al., 2006; Young & Lenné, 2010).

What are the effects of distraction on traffic performance?

In recent years many studies have been made into the effects of distraction on traffic behaviour. These are largely laboratory tests in which a driving simulator, a virtual environment, or computer animations were used. Sometimes observations or road experiments are carried out.

All these studies indicate that distraction affects some of the essential aspects of the traffic skills.  For example, distracted drivers swerve more, which indicates reduced vehicle control. Furthermore, road users who are occupied with distracting activities also miss information. This usually happens because they no longer have their eyes on the road, for instance while searching for a particular piece of music on a portable music player. But also when their eyes are focused on the road, cognitive distraction, for example caused by a phone conversation, can be responsible for relevant information not being perceived. Furthermore, distracted road users often have a slower reaction to changes in the environment. Pedestrians who are conducting a telephone conversation, for instance, take more time to start crossing the road (Neider et al., 2010). Distraction also leads to more errors. For example, an experiment in a virtual environment showed that pedestrians with a portable music and media player more often halted for a stopped car when crossing a road than pedestrians who do not use such a device. Distraction often leads to a lower driving speed and increased headway. In this way the road user seems to compensate for the effects of distraction. In principle, a greater headway distance and a reduced speed are good for road safety (see also the archived SWOV Fact sheets Headway times and road safety and Speed and speed management). However, when a reduction in speed leads to great speed differences between distracted drivers and other road users, this may be the cause of conflicts (see also the archived SWOV Fact sheet Sustainably Safe road traffic).

Other than the various negative effects, some sources of distraction can sometimes also have positive effects on the traffic task. For example, music can reduce stress and aggression and help drivers to remain alert. Listening to music seems to have few other negative effects (see for example Salvucci et al., 2007), except when it is emotional music (Pêcher et al., 2009), or loud or high tempo music (De Waard et al., 2011).

How does distraction influence crash involvement and risk?

It is not easy to determine the exact risk of crashes due to different distracting activities. The fact is, it is difficult to establish causality. For 905 crashes, a large 2016 American study recorded on film what the driver did before the crash. This showed that in 68% of the crashes the driver was distracted. Types of distractions that were found to occur frequently, were, among others, talking to a passenger, telephone use and operating devices (Dingus et al., 2016). However, some studies report lower estimates. Most earlier studies estimate that distraction plays a role in the occurrence of between 5 and 25% of all car crashes (Hurts et al., 2011). The diversity of data is, among other things, the result of different definitions of distraction used in the studies, and of the method used for risk estimation.

Differences in definition and research methods also make it hard to determine precisely how dangerous various distracting activities are. Many of these activities seem to increase the risk of crashes. American Naturalistic Driving studies (ND studies) indicate that particularly those activities that cause the strongest visual distraction are the most dangerous. These are mainly activities like typing or reading text messages (texting), but also entering a phone number or reaching for objects; these activities take the eyes off the road for a considerable amount of time. In older ND-studies it is a problem that they also include near-crashes, because the number of actual crashes was too small for statistical analysis. The meaning of distraction can be different in near-crashes and in actual crashes.

In the recent American ND study by Dingus et al. (2016) the sample was sufficiently large to calculate the crash risk of several  kinds of distraction based on actual crashes. 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 1.4 for the activity 'talking with passengers' means that the risk of an crash is 1.4 times higher than when one does not talk to passengers. 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 lengthy looks at objects outside the car is 7.1, but it is at least for 95% certain that the odds ratio is greater than 4.8 (the first number in parentheses) and smaller than 10.4 (the second number).
The right-hand column shows the prevalence of the activity. 'Talking with passengers' has a prevalence of 14,58%. This means that  14.58% is the average proportion of the time drivers talk with passengers.

Tabel 1. The odds ratio’s (‘relative risks’) and prevalences of some of the distracting activities of drivers (Dingus et al., 2016).

 

The study by Dingus et al. (2016) confirms that visual distraction is particularly dangerous. This is distraction by, for instance, lengthy looks at objects outside the vehicle or being occupied with texts on paper or a tablet (for more information about actions  with a mobile phone, see SWOV Fact sheet Use of the mobile phone while driving).

Note the odds ratio of 0.5 for 'children in the rear'. This means that one drives more safely when responding to children in the rear than when one does not. Presumably this is due to the fact that one already drives carefully when one carries children, and is extra careful when one is distracted by the children.

Little is known about the risk of different activities among cyclists and pedestrians, especially if it concerns distraction that is not caused by all kinds of modern technology. Self-reported data indicated that the use of media devices increases the risk of a crash. More information about the crash risk associated with the use of electronic devices while walking and cycling can be found in SWOV Fact sheet Phone use by cyclists and pedestrians.

Which measures can be taken?

Some measures to prevent distraction in traffic have already been taken. For example, it is prohibited by law to conduct handheld telephone conversations and standards have been set for advertising billboards alongside the road.  Furthermore, the dangers of being distracted by electronic devices (mobile phone, smartphone and navigation system) while driving are pointed out to road users in the Netherlands in the public information campaign ‘Don’t be distracted’.

Furthermore, attention could be given to the dangers caused by distraction during driver training. A promising intervention, for instance, is a training developed by Pradhan et al. (2011) that makes drivers aware of the dangers of distraction and trains drivers not to take their eyes off the road for longer than two seconds when operating a device. In addition, technology itself could be adapted. All in-vehicle devices could be given a user-friendly design so that it would require less attention from the driver (this is one of the recommendations formulated by the European Commission (EU, 2008). Another example is the integration of different applications in one system which (for instance by monitoring the mental effort made by the driver) can determine which message is the most important for the driver at that specific point in time. Another possible measure is the development of warning systems that inform the distracted driver or sometimes even intervene in a risky situation (see also SWOV Fact sheet Intelligent Transport Systems (ITS) and road safety). Furthermore, it can be made impossible to operate devices, e.g. navigation system, while driving. Mobile phone use, handsfree as well as handheld, can be prevented as much as possible, for example with the ‘Auto Reply App’ (for more information about the ‘Auto Reply App’ see SWOV Fact sheet Use of the mobile phone while driving). Finally, the road environment could be adapted in such a way that road users can stop safely in many locations, for example to use their phone or to operate the navigation system.

Presently, too few evaluations of the effectiveness of all kinds of measures have been carried out to prevent distraction in traffic. For this reason a combination of measures seems to be a good solution. This can be found in legislation, enforcement, and change in the manner of thinking about which traffic behaviour is socially acceptable.

Conclusion

Distraction appears to be a factor in a considerable number of crashes and therefore appears to be a safety problem. The growing presence of electronic devices in traffic threatens to increase the size of the problem. Research indicates that many drivers, but also cyclists and pedestrians, are occupied with all kinds of activities that are not relevant for the traffic task, for instance, listening to music, using the mobile phone, or texting. Although distraction has clearly been found to have negative effects on traffic behaviour, it is not easy to prove the causality between distraction and the number of crashes. The most elaborate and most recent American study estimates that distraction (phone use or other) plays a role in the occurrence of between 5 and 25% of all car-crashes. Many distracting activities seem to increase the risk of a crash. Recent Naturalistic Driving studies show that activities like texting which draw the eyes off the road for a longer period of time are the most dangerous. The present state of our knowledge, however, is insufficient to determine the exact degree to which various distracting activities increase the risk of crashes. Many measures can be taken to counteract the negative effects of distraction in traffic, for example public information, education, or technical facilities that make it impossible to operate devices like the navigation system or the mobile phone when in traffic.

Publications and sources

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.

Goldenbeld, C., Houtenbos, M. & Ehlers, E. (2010). Gebruik van draagbare media-apparatuur en mobiele telefoons tijdens het fietsen; Resultaten van een grootschalige internetenquête. R-2010-5. SWOV, Leidschendam.

Goldenbeld, C., Houtenbos, M., Ehlers, E. & Waard, D. de (2012).The use and risk of portable electronic devices while cycling among different age groups. In: Journal of Safety Research, vol. 43, nr. 1, p. 1-8.

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

Hurts, K., Angell, L.S. & Perez, M.A. (2011). The distracted driver: mechanisms, models and measurement. In: Reviews of Human Factors and Ergonomics, vol. 7, nr. 1, p. 3-57.

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.

Lee, J.D., Young, K.L. & Regan, M.A. (2008). Defining driver distraction. In: Regan, M.A., Lee, J.D. & Young, K.L. (red.), Driver distraction: theory, effects and mitigation. CRC Press, Taylor & Francis Group, Boca Raton, Florida, p. 31-40.

McEvoy, S.P., Stevenson, M.R. & Woodward, M. (2006). The impact of driver distraction on road safety: results from a representative survey in two Australian states. In: Injury Prevention, vol. 12, nr. 4, p. 242-247.

Neider, M.B., McCarley, J.S., Crowell, J.A., Kaczmarski, H., et al. (2010). Pedestrians, vehicles, and cell phones. In: Accident Analysis and Prevention, vol. 42, nr. 2, p. 589-594.

Pêcher, C., Lemercier, C. & Cellier, J.-M. (2009). Emotions drive attention: Effects on driver’s behaviour. In: Safety Science, vol. 47, nr. 9, p. 1254-1259.

Pradhan, A.K., Divekar, G., Masserang, K., Romoser, M., et al. (2011). The effects of focused attention training on the duration of novice drivers' glances inside the vehicle. In: Ergonomics, vol. 54, nr. 10, p. 917-931.

Ranney, T.A., Mazzae, E., Garrott, R. & Goodman, M.J. (2000). NHTSA driver distraction research: past, present, and future. National Highway Traffic Safety Administration NHTSA, Washington D.C.

Regan, M.A., Lee, J.D. & Young, K.L. (red.) (2008). Driver distraction: theory, effects and mitigation. CRC Press, Taylor & Francis Group, Boca Raton, FL.

Rijksvoorlichtingsdienst (2010). "Hallo jongen, met je moeder" Campagne ‘Afleiding in het Verkeer & Rij Voorbereid (L41). Eindrapportage campagne-effectonderzoek. Rijksvoorlichtingsdienst, Ministerie van Algemene Zaken, 's-Gravenhage.

Salvucci, D.D., Markley, D., Zuber, M. & Brumby, D.P. (2007). iPod distraction: effects of portable music-player use on driver performance. In: Proceedings of the Special Interest Group on Computer-Human Interaction SIGCHI conference on Human Factors in Computing Systems HFCS, 28 April - 3 May 2007. San Jose, California, p. 243-250.

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

Stutts, J.C., Feaganes, J., Reinfurt, D., Rodgman, E., et al. (2003). Distractions in everyday driving. AAA Fundation for Traffic Safety, Washington, D.C.

Stutts, J., Feaganes, J., Reinfurt, D., Rodgman, E., et al. (2005). Driver's exposure to distractions in their natural driving environment. In: Accident Analysis & Prevention, vol. 37, nr. 6, p. 1093-1101.

Waard, D. de, Edlinger, K. & Brookhuis, K. (2011). Effects of listening to music, and of using a handheld and handsfree telephone on cycling behaviour. In: Transportation Research Part F, vol. 14, nr. 6, p. 626-637.

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.

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Updated

27 Jun 2017