Experiment: An experiment was conducted to assess the distraction potential of secondary tasks performed using in-vehicle systems (radio tuning, destination entry) and portable phones (10-digit dialing, selecting contacts, text messaging) while driving. One hundred participants, ages 25-64, completed a single session in which they drove a low-fidelity (PC-based) simulator while performing the secondary tasks. The phone tasks were performed with two smart phones, one with a touch screen interface (iPhone) and one with a hard button interface (Blackberry). The Dynamic Following and Detection (DFD) driving protocol, which combines car-following with target detection, in which drivers responded to simple visual targets presented in the simulated roadway display, was used. Each combination of primary (driving) and secondary task was performed during a single 3-minute drive. Driving performance metrics included: lane position variability, car-following delay, target-detection accuracy and targetdetection response time. Results: Text messaging was associated with the highest level of distraction potential. Ten-digit dialing was the second most distracting task; radio tuning had the lowest level. Although destination entry was no more demanding than radio tuning when task duration effects were eliminated with DFD metrics, it exposes drivers to more risk than radio tuning and phone tasks due to its considerably longer duration. Modest differences between phones were observed, including higher levels of driving performance degradation associated with the touch screen relative to the hard button phone for several measures. Additional analyses demonstrated that the way in which task duration is considered in the definition of metrics influenced the outcomes of statistical tests using the metrics. The results are discussed in the context of the development of guidelines for assessment of the distraction potential of tasks performed with in-vehicle information systems and portable devices. Additional analyses were conducted to compare the DFD and Alliance and decision criteria in a simulated compliance scenario. With the large sample size (N = 100), both protocols supported the conclusion that neither text messaging nor 10-digit dialing is suitable for combining with driving; however, when a smaller (N = 40) sample was used, the protocols led to different conclusions. Additional analyses found that for, using just the vehicle performance metrics (not the eye glance metrics), samples of 20 participants did not provide sufficient statistical power to differentiate among secondary tasks. Driver age had significant effects on both primary and secondary task performance; younger drivers completed more secondary task trials on a given drive, with relatively less primary task interference than older drivers. Tests conducted using samples with wide age ranges (25-64) required larger samples to compensate for reduced homogeneity relative to samples with narrow age ranges. Half of the participants were given specific monetary incentives...

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An experiment was conducted to assess the distraction potential of secondary tasks using the Alliance of Automotive Manufacturers' Principle 2.1B verification procedure implemented using specifications obtained from an Alliance member company. Secondary tasks included radio tuning, destination entry, 10-digit dialing, dialing via contact selection, and text messaging were performed using the original equipment systems of a 2010 Toyota Prius V and an iPhone 3GS smart phone. Sixty-three participants 35 to 54 years old drove a low-fidelity, PC-based simulator while performing the secondary tasks. The driving scenario required participants to maintain a 150-ft following distance behind a lead vehicle that was traveling at a constant speed of 50 mph. Alliance driving performance metrics included lane exceedance frequency and the standard deviation (SD) of car-following headway. Text messaging was associated with the highest levels of driving performance degradation on both Alliance Principle 2.1B metrics, followed by destination entry. Radio tuning had the lowest levels of driving performance degradation. The two phone dialing tasks (contact selection and 10-digit number dialing) had approximately equivalent amounts of driving performance degradation. Both Alliance Principle 2.1B metrics were correlated with task duration. Use of a duration-adjusted metric revealed that text messaging was significantly more demanding than other secondary tasks and that other differences between tasks were due primarily to differences in task duration. Results using smaller sample sizes were consistent with the expected loss of statistical power inherent in the use of small samples. Differences were also apparent between replications of samples of the same sizes. Based on the results of the current study, neither 20 nor 30 participants is sufficient to obtain consistent test outcome results. Two sets of analyses compared present study outcomes with those from a previous study, which used a Dynamic Following and Detection (DFD) protocol that provided both Alliance Principle 2.1B and other vehicle control and visual target detection metrics. Results from the two Principle 2.1B verification procedure implementations were not consistent, despite the fact that both implementations were consistent with Alliance specifications. Differences in driving (car following) task demands appear to have contributed to this finding. The second comparison with previous study results used different metrics and their respective decision criteria. Decisions concerning the acceptability of specific number/text entry tasks based on Alliance Principle 2.1B metrics were not consistent with those made using DFD metrics. The two protocols provided consistent results on 7 of 10 planned comparisons. Different conclusions derive from three factors: (1) driving behaviors represented by the metrics, including target detection in the DFD protocol, (2) metric construction, reflecting the differential treatment of task duration, and (3) decision criteria. Alliance (durat...