“The Driver Workload Function” (DWF) model, developed by Denso and University of Iowa, was created to quantitatively measure the performance of HMI design.
DWF is a predictive model developed by adapting the Cognitive Avionic Tool Set (CATS) for a series of driving tasks.
Five tasks were completed for each Multi-modal Interface for Drivers concept (MMID): change radio volume, change temperature, change fan speed, change fan mode, and change radio to a preset station. Physiological measurements used to create the DWF include eye tracking data, electroencephalogram (EEG), and electrocardiogram (ECG). A single performance measure, time to complete task was also included. This study sought to establish a quantitative method for evaluating the Automotive HMI performance at task level.
The numeric value of driver workload for each task is the key data to determine the performance of the HMI system by identifying the typical driving workload, the addition workload from HMI interaction and available resource the driver has to allocate to unexpected situation (avoid crash accident). More than 50 variables were measured and then evaluated for the DWF model. The DWF model was created using a stepwise regression process. The confidence in predictability model measured by regression square value was in the range of 80 to 90% for pilots. The initial automotive value was in the range of 20%.
Participants in Phase I of the study consisted of 21 drivers with ages ranging from 22 to 50. In Phase II, 10 drivers with ages ranging from 19 to 57 were recruited.
The main vehicle used for both phases of the study was a Lexus LS-430 instrumented to have physiological monitoring capabilities. Additional modifications were made to the vehicle in order to accommodate the new MMID. The central instrument cluster was replaced with a programmable LCD display. During the experiment, GUI 1 or GUI 2 was displayed on the screen. Two Reconfigurable Haptic Joysticks (RHJs) were added to the steering wheel as seen in on the right side of Figure 1. The Dual Touch Function