Second-Generation UMTRI Coding Scheme for Classifying Driver Tasks in Distraction Studies and Application to the Avoidance System (ACAS) Field Operational Test (FOT) Video Clips

摘要

This report describes the development of a new coding scheme to classify potentially distracting secondary tasks performed while driving, such as eating and using a cell phone. Compared with prior schemes (Stutts et al., first-generation UMTRI scheme), the new scheme has more distinctive endpoints for tasks and subtasks, is less subjective (e.g., no 'high involvement' eating), includes codes for activities absent from prior schemes (e.g., chewing gum), and more closely links subtasks to visual, auditory, cognitive, and psychomotor task demands. The scheme has codes for 12 tasks (use a cell phone, eat/drink, smoke, chew gum, chew tobacco, groom, read, write, type, use an in-car system, internal distraction, and converse) plus codes for drowsiness. The scheme takes several factors into account, such as where the driver is looking, where the driver's head is pointed, what the driver's hands are doing, the weather, and the road surface condition. Each main task was divided into 3 to 17 subtasks (e.g., groom using tool, reach and get phone). This scheme was used to code video clips of drivers' faces from the ACAS field operational test. In the first pass, 2,914 video clips were coded (for task, drowsiness, weather, and road) using custom UMTRI software. In the second pass, a sample of 403 distracted and 416 nondistracted clips were coded frame by frame (15,965 frames) for the subtasks performed, gaze direction, and where the head was pointed.Two analysts rated the visual, auditory, cognitive, and psychomotor demands of 68 subtasks (e.g., prepare to eat/drink, converse on the cell phone) performed while driving. Ratings were relative to anchors from the U.S. Army IMPRINT modeling tool (0-to-7 scale). Video clips of those subtasks were sampled from the advanced collision avoidance system (ACAS) field operational test (FOT) database, a naturalistic study of driving previously performed by UMTRI. Key findings were: (1) The most demanding tasks were dialing a phone, answering a phone, lighting a cigar or cigarette, dealing with pet and insect distractions, dealing with spilled drinks and food, typing with 2 thumbs, and drinking from a cup, in that order. (2) Demand levels within subtasks were moderately correlated (visual-cognitive=0.68, visual-psychomotor=0.48, cognitive-auditory=0.42, cognitive -psychomotor=0.34) or close to 0. (3) In terms of these ratings, cognitive demands, both per unit time and when weighted by exposure, were consistently double the value of others. (4) Demands varied to a limited degree among road types. (5) There were consistent differences in demand due to driver age and sex. Researchers are encouraged to use the demand ratings provided and extend them to other tasks so tasks can be compared across experiments.