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This study assessed the driver workload imposed by a text messaging system and cellular phone on heavy vehicle drivers under various driving conditions. Sixteen (1 6) professional commercial vehicle operation (CVO) licensed drivers drove an instrumented heavy truck over a 4-hour period on public roads under various conditions of ambient lighting (day or night), traffic density (light or heavy), and road type (divided or undivided). Within driving condition combinations, various levels of text message reading, cellular phone dialing, radio tuning, and communications dialogue were completed by the driver. Continuous measures were taken of visual allocation, steering and accelerator activity, speed maintenance and lane-keeping performance. Results of in-vehicle device use are presented and provide insights into useful workload measures and methods, as well as a contribution to the literature on cellular phone and invehicle text messaging system ergonomics.

This report reviews literature on workload measures and related research. It depicts the preliminary development of a theoretical basis for relating driving workload to highway safety and a selective review of driver performance evaluation, workload evaluation in driving contexts, and risk-taking and risk adapation behavior. An actuarial approach to establish the safety relevance of workload measures in discussed in conjunction with a driver resources allocation model of in-cab device workload. The report concludes with the presentation of a driver resources-based taxonomy of in-cab tasks and candidate workload measures and their potential sensitivity to tasks described in the taxonomy. 17.

This report consists of an empirical establishment of heavy vehicle driver baseline performance data. Researchers interested in highway safety have called out the need for rudimentary workload data so that they might have a basis for comparison of workload associated with particular in-cab high technology devices. Thirty (30) professional drivers participated and were asked to perform a series of tasks during over-the-road drives involving both open road driving and close car following in both day and night conditions. The requested tasks included looking at right and left mirrors, adjusting CB volume, changing CB frequency, manually tuning the radio, adjusting radio volume, reading clock, reading air pressure, adjusting the heating or air conditioning, and calculating available driving hours. Drivers were measured with respect to visual allocation; steering, accelerator, and brake inputs; speed and headway maintenance; and lanekeeping. Results indicated that, to a varying degree, visual allocation measures, several steering measures, speed variance, and several lane position measures are preferable measures for further workload assessment.

This technical report consists of a collection of task analytic data to support heavy vehicle driver workload assessment and protocol development. Data were collected from professional drivers to provide insights into the following issues: the meaning of the term 'workload' to heavy vehicle drivers (N = 41 drivers interviewed); the demand placed on drivers (N = 55) by various drving conditions using a psychological scaling approach; the safety criticality and difficulty of selected standard driving tasks (N = 30 drivers assessed); the perceptual, motor, and cognitive loads imposed by various tasks while on the road under various conditions (N = 9 drivers observed over-the-road during revenue runs); and a preliminary analysis of the key features of generic high-technology in-cab devices. When professional truck drivers speak of workload, they tend to talk in terms of time stress or stress caused by delays to their schedules. Various driving conditions were unidimensionally scaled in terms of order of impact on drivers, and those results are presented and discussed. Safety criticality and difficulty assessment results provided some validation for the scaling outcomes. Visual allocation measures in this study suggested that the use of common-in-cab tasks would serve as baseline measures, based on the revenue runs. Finally, key features considered in evaluating voice communication systems, vehicle navigation and route guidance systems, single/integrated displays, and text communicaton devices were determined.