Track testing was conducted on the high-speed test track of Ford Motor Company’s Michigan Proving Ground in Romeo, Michigan. The test track was a 5-mile oval with 1-mile straightaways and 2,500-foot radius curves. The track has 5 lanes, each 12 feet wide on the straightaways that transition to 13 feet wide on the curve sections. The three-car platoon was given access to lane 2, which was unbanked on the curve sections.
Procedures used for on-road testing were applied to track testing as well. Two laboratory stations were set up at the proving grounds for task training and individual differences testing purposes. No surrogate data was collected at the test track. The participants were greeted at the lobby at 7 a.m. and were escorted to the testing site by the experimenters. The order of protocols was similar to that of the on-road segment; however, in this segment all 23 DWM tasks were used in the data collection process, compared to the 16 that were used in the on-road testing. Sufficient time was provided for the participant to drive around the track and get a feel for the vehicle dynamics and the controls.
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Track testing began after lunch and continued through the morning of Day 2. There were six blocks of tasks for track testing. Each block contained all 23 tasks. Each task was assigned one and only one OED stimulus per trial. The OEDs and the testing protocols used in the test track were identical to the ones used on the on-road segment. The OEDs were explained to the participant and examples were provided during the practice drive. Track trials were conducted as the final venue for data collection. Experience during the on-road trials suggested certain procedural efficiencies that could be applied to the track venue. Procedural simplification was in three areas. Track testing would use only six blocks, three to cover all tasks and three blocks for replication. Each trial would have one and only one OED event scheduled for it. The track testing would schedule all three replication blocks only after all three blocks of original blocks were completed. The reduced number of blocks and revised OED schedule were more readily executed on the track than the eight blocks used for the on-road trials. The notion of scheduling replication blocks only after all tasks had been tested once was due to experiences with weather. The goal was to have at least one trial per task per OED scheduled in the event that rain cut short the testing session. Road testing had replications in blocks back-to-back. A 10-minute break was provided after each block in addition to a one-hour lunch break.
Day 2 testing for the participant was the same as the on-road venue.
2.1.3 Laboratory Venue
Laboratory testing examined both performance testing and subjective workload assessments. Six different surrogate methods for performance testing of tasks were investigated in the laboratory. Tasks were assessed twice with each method. Brief descriptions of these methods are provided below and details of the methods are provided in Appendices D and R.
Static Time This method provided a static time metric. Measurements were taken of the total time needed to complete each variable-duration visual-manual DWM task when performed alone, without any concurrent task or any interruptions
Occlusion This method provided a total shutter open time (TSOT) metric. Measurements were taken during task performance of the TSOT needed to complete a visual-manual DWM task when performed wearing occlusion goggles. These goggles were computer-controlled to open for 1.5 seconds and close (go opaque) for 2.0 seconds cyclically until the task was done.
PDT-Alone This method provided percent missed detections and reaction time metrics. Measurements were taken during DWM task performance of the number of missed detections and the reaction time of detections to a peripheral detection task (PDT) light. The PDT light was a high-intensity spot of laser light. It was briefly and periodically presented on a wall- mounted projection screen in front of the test participant during task performance. The participant pressed a button with the left hand if the PDT light was noticed. Multiple PDT stimuli were presented during task performance, more for longer tasks. All DWM tasks were assessed.
Chapter 2 Study Design Overview
PDT with STISIM
This test provided task duration, lanekeeping, and speed maintenance measures while driving and performing DWM tasks. Measurements of driving performance in the Systems Technology Inc. (STI) fixed-base, part-task simulator were taken as subjects concurrently drove the simulator and performed requested tasks. The simulation involved following a lead vehicle that traveled at constant velocity at a consistent self-selected following distance. The PDT stimuli described above were also concurrently presented during the drive. All DWM tasks were assessed.
Sternberg-Visual
This method provided percent error and reaction time metrics, as well as percent missed detections. A participant memorized three symbolic road signs (e.g., T-intersection, traffic merging from right, road enters from left, etc.) prior to the start of a trial. During CAMP task performance, individual symbolic road signs were periodically and briefly presented on an LCD display mounted ahead of the participant. When noticed, the participant was instructed to press one button with the left hand if the presented road sign was from the memorized set (a positive-match probe) or different button with the left hand if the presented road sign was not from the memorized set (a negative-match probe). Multiple probe signs were presented sequentially on the LCD display, more for longer tasks. Approximately equal numbers of positive and negative probes were scheduled for presentation in a random order. The road signs for the Sternberg-Spatial test were of road geometry and did not involve alphanumerics. All DWM tasks were assessed.
Sternberg-Verbal
This test was identical to the Sternberg-Spatial test except the memorized signs and subsequent probes were of alphanumeric signs like state route numbers. All DWM tasks were assessed.
Participants also completed a variety of subjective assessments of tasks:
Operator Workload (OWL)
A univariate scale of overall task workload from 1 (low) to 100 (high). The participant rated a given task against this fixed scale. All tasks were assessed except the Just Drive task.
Chapter 2 Study Design Overview
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