As multimedia devices like smartphones and tablet-PCs become more frequently used while driving, the potential problems of those non-driving related activities are rising and are getting into public awareness. Beyond simply making phone calls, these devices are allowing a number of other activities such as texting, writing and reading emails and searching the web. Scientific studies on the distraction effects of such new functionalities in the vehicle and their potential endangerment of road safety are therefore of special importance. This report describes two simulator studies on this topic. Besides methodological issues, the results are discussed with regard to the impact of those non-driving related tasks on road safety. In the first study conducted in the driving simulator of the Federal Road Research Institute (BASt), 39 participants drove in the simulator while performing a secondary visual-motor task. One group of drivers had to work on this task in specific traffic situations (block-condition), while the other group was free to decide when to work on this task (self-regulatory condition). Driving without distraction was used as comparator. For the first group, distraction was associated with high decrements in driving performance (especially in lane keeping). No impact was found on the number of collisions, probably because of the lower driving speeds while being distracted (compensatory behavior). For the self-regulatory group only very little impairments in driving performance were found. Drivers engaged less in the secondary task in critical situations. Implications of this study are discussed with consideration of specific self-regulatory strategies and moderating factors. In the second simulator study conducted at the Würzburg Institute for Traffic Sciences (WIVW GmbH) with a sample of 48 drivers, several non-driving related activities on a smartphone were investigated, such as sending and receiving text messages, dialing phone numbers and searching the web. 24 drivers performed these tasks in a free non-integrated context, which means that text and numbers had to be entered directly on the smartphone mounted in a dashboard mount. Additional 24 drivers performed these tasks in an integrated context which allowed using voice recognition and text-to-speech. Internet access was restricted to selected contents. The effects of these non-driving related activities on eye glance behavior, driving performance and safety were assessed both in a standardized car-follow scenario as well as on a complex driving course containing different traffic scenarios. The results showed that driving performance was more impaired by activities imposing high visual-motoric demands, such as reading and writing text messages. Therefore, writing text messages or emails on the phone as well as browsing mobile news pages is considerably impairing. Overall, if an integrated control solution was used, driving was less impaired as visual-motoric distraction is reduced. Receiving and sending text messages by voice control distracted drivers less, so that lateral control was less impaired and less driving errors occurred. In addition driving performance was rated as being less impaired. Drivers stated that they would accept the integration of their smartphone into the in-vehicle information system by a dedicated car-application with its benefits and restrictions. Despite the observed impairments in driving performance, no serious effects of these non-driving related activities on safety could be found. The number of critical situations (endangering other road users, crashes) did not rise in a considerable way due to the interaction with these tasks. This might be explained by an increase in compensational effort (e.g. increased distances to leading vehicles, reduced driving speed). In very time critical situations drivers completely refrained from performing these tasks. In addition, it became obvious that drivers adapted their non-driving related activities to the performance demands of the traffic situation. (Author/publisher)
Abstract