Mobile phone use while driving is a major concern for traffic safety. Various studies indicate negative effects of distracted driving and recent Naturalistic Driving studies report substantial increase in crash risk of mobile phone use while driving. The increasing level of vehicle automation is likely to further increase phone use behind the wheel, as the automation takes over part of the driving task drivers are likely to experience boredom and feel more confident to get involved in other activities such as phone use. This may further increase the distraction related accidents on our roads. However, the extent to which this further increases depends largely on the drivers’ level of self-regulation of risk, the timing of engagement in phone activities in relation to the driving context. The objective of this study was to investigate if drivers self-regulate their mobile phone use, specifically focussed on the visual manual (VM) task which is associated with the largest increase in risk, while driving in relation to different driving contexts. For this study naturalistic driving data was analysed of Dutch car drivers collected in the UDRIVE project. The results show that Dutch drivers spent over 9% of all driving time engaging in mobile phone related tasks, including calling and VM tasks such as texting. Drivers used their mobile phone significantly less when a passenger was present. Also, significantly more VM tasks were initiated during standstill than for the other speed categories. In addition, on rural roads relatively less time was spent on VM tasks and on highways relatively more time was spent on VM tasks. Overall the results show that the driving context seems to influence the initiation and involvement in VM tasks, which is an indication that drivers self-regulate this behaviour.

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Within the UDRIVE project, a rich cross-European naturalistic driving database was created which includes everyday driving data on car and truck drivers and powered two-wheeler riders. The database provides extensive, reliable insights into driving behavior in real traffic as a foundation for improving the safety and sustainability of European road traffic. This paper discusses the characteristics of the data in the UDRIVE database—elucidating key methodological choices and presenting a selection of results to date. A priority of the study design was obtaining in-depth information on driving behavior, permitting the exploration of diverse research questions. A tailor-made data acquisition system collected very comprehensive data. A total of 287 drivers/riders participated. The sample size restricts the addressable research topics to common behaviors in everyday driving and limits the generalizability of results. However, the data are extensive and promising analyses have already been performed. The results show differences between European countries for distracting activities, seatbelt use, and looking behavior towards cyclists at urban intersections. Moreover, it shows that European drivers engage less in mobile phone use than U.S. drivers. It is likely that European drivers differ in other ways, also—highlighting the dataset's value for developing and implementing targeted safety measures, for the E.U. and its individual countries. Based on the comparison of the different studies, the paper introduces the general conceptual framework for naturalistic driving studies, providing insight in the relation between the scope of a naturalistic driving study and the key methodological choices on sample selection and data acquisition system.

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Naturalistic driving studies are increasingly applied in different shapes and sizes. The European project PROLOGUE has investigated the value and feasibility of a large-scale naturalistic driving study in Europe. Within PROLOGUE several pilot studies have been conducted in different countries. The Dutch field trial investigated the value and feasibility of adding site-based observations to in-vehicle observations.

In this trial, one intersection was equipped with cameras for site-based observation. Additionally eight cars were equipped of drivers crossing this intersection regularly. On this small scale, combining the two observation methods turned out to be technically feasible. It was possible to recognise the instrumented vehicles in the site-based video data, to match cases from the different observations and the speed measures from the separate studies appeared to be similar.

The value of combining these two observation methods lies in the possibility to enrich the data from one study with complementary data from the other study. The study illustrated that each type of observation has its unique values. From in-vehicle data it is possible to look in detail at the driving behaviour of the participants over time and in different situations. The site-based study offers information about the position and speed of other road users surrounding the participant's vehicle, including vulnerable road users such as cyclists and pedestrians. Two values of adding site-based observations to in-vehicle observations were identified: to obtain more in depth understanding and to relate the behaviour of participants of the naturalistic driving study to behaviour of the full population of drivers (non-participants).

For a future (large-scale) naturalistic driving study two research topics are identified that could benefit from these complementary observations: driving behaviour in relation to specific infrastructure and the interaction between drivers and vulnerable road users.@en