Driver distraction and inattention in its various forms is thought to play a role in 20-30% of all road crashes (Wang, Knipling & Goodman, 1996). Distraction is caused by a competing activity, event or object from inside or outside the vehicle. Safety problems related to driver distraction are expected to escalate in the near future as more technologies become available for use in motorized vehicles. A relatively new technology, already widely available and accepted, is the mobile phone. While it is clear that mobile phones enhance business communication and increase personal convenience, use of mobile phones while driving has become a road safety concern. The vast majority of drivers (60 to 70%) report using their mobile phone at least sometimes while driving, and it is estimated that at any given moment during the day, 1 to 4% of the drivers is using a mobile phone. The mobile phone distracts drivers in two ways: it causes physical distraction and cognitive distraction. Physical distraction occurs when drivers have to simultaneously operate their mobile phone (i.e. reach, dial, hold) and operate their vehicle. Cognitive distraction occurs when a driver has to divert part of his/her attention from driving to the telephone conversation. However, the ability to divide one’s attention between two simultaneous tasks is limited. Mobile phone use while driving could therefore negatively affect driving performance. The results of epidemiological studies strongly suggest that using a mobile phone while driving can increase the risk of being involved in a road crash up to four times. The possible ‘impairment potential’ of mobile phone use while driving has been the focus of various behavioural studies. This review only includes studies published from 1999, because studies published prior to 1999 have already been analysed in a previous SWOV report (see Oei, 1998). For the purpose of this review, based on the research methodology (degree of realism and closeness to real-world driving), the analysed studies are grouped in: 1. Simulator studies 2. Closed-track studies (test-track studies) 3. Studies on the real road The distractive effects of mobile phone use depend on the momentary context of driving. Phone use during undemanding driving periods may not seem to be a problem. However, both the demands of the driving context and the content and demands of the mobile phone conversation play a role in this process. The level of complexity of the phone conversation (its cognitive demands) is the important factor that also determines the extent of the effect of the phone conversation on driving performance. Although studies differ with regard to the extent of behavioural changes found, most of them confirmed the fact that using a mobile phone while driving negatively affects various aspects of driver performance. The following effects have been demonstrated: - Slower reactions to traffic signals and more frequently missed signals - Slower braking reactions with more intensive braking and shorter stopping distances - Reduced general awareness of other traffic - More risks in decision making, - Compensatory behaviour Hands-free versus handheld use of the mobile phone remains one of the most commonly investigated features. The vast majority of studies report that hands-free phoning does not have a significant safety advantage over handheld phoning. Although handheld units add to the driving task due to the need for manipulation, the most important negative factor of mobile phone use is the same for both types of phone — the diversion of attention from driving to the conversation itself. Different countries have introduced various kinds of legislation aimed at restricting the use of mobile phones. The most common legislative measure is the ban on handheld mobile phones in vehicles. Other measures include prohibiting the use of the mobile phone for drivers in some special driver categories, such as drivers with special responsibilities (e.g. school bus drivers) or young drivers who only have a learner's licence. There is still very little data on the effectiveness of these legislative measures. There are indications that although the short-term effects could be a 50% reduction in mobile phone use, the long-term effects (after one year) are far less positive. It has been recognised that the effectiveness of legislation could be increased if supported by publicity campaigns and a broadly based educational campaign to promote responsible use of mobile phones while driving. In order to better determine, control and reduce the effects of mobile phone use on road safety, this report concludes with the following recommendations: - Identify the extent of drivers’ use of mobile phones more precisely in order to generate more exact data on the risk of mobile phone use while driving. - Record mobile phone use in accident reports in order to produce a truer estimate of the number of mobile phone crashes in the total number of crashes. - Make drivers more aware of the dangers of mobile phone use and other various distracting activities. - Design the Human-Machine Interface as ergonomically as possible. - Develop precise criteria and methodologies for assessing the safety implications of in-vehicle information systems (IVIS), including mobile phones. - Base the legislation of mobile phone use on scientific evidence. - Support company policies like those imposing a complete ban on the use of mobile phones while driving and other kinds of policies contributing to the corporate safety culture. - Use the 'technology against technology' principle: technology could also provide the answer, at least partly, to solving the problem of driver distraction.
Use of mobile phones while driving - effects on road safety
A literature review