On-demand driver vigilance enhancement without explicit drowsiness detection-Further analysis of the pilot study...

A new active safety concept that engages the driver's psychosensory pain-processing mechanism to automatically trigger vigilance enhancement on-demand was proposed in Chang (2012). This concept is based on the hypothesis that a human's pain threshold will decline as he or she becomes drowsy, consequently triggering the vigilance enhancer. The objective of this pilot study was to develop methods to test this hypothesis, the results of which could lead to further refinement of the hypothesis and methods, with the ultimate goal of developing new active safety concepts that exploit the driver's endogenous psychosensory pain-processing mechanisms. Preliminary results from a pilot study designed to test this hypothesis were presented in Chang (2016). This article presents further analysis of the pilot study data.

Perceived pain responses of six healthy male participants were measured when their vigilance would be under stress. A time-varying thermal grill illusion (TGI) of pain was created using a custom steering wheel with an array of Peltier elements held in the participant's palm. The participant's pain responses to the TGI stimulus were recorded while changes in his vigilance were monitored using pre- and post-session Psychomotor Vigilance Task (PVT) tests, in-session Percent Eyelid Closure (PERCLOS), and subjective Karolinska Sleepiness Scale (KSS) ratings. The probability of pain response versus TGI temperature stimulus and vigilance measures were then estimated using logistic regression analysis.

The results indicate that the probability of pain response is correlated with the temperature stimuli and the vigilance state. The pain threshold tends to move up or down versus KSS depending on the participant for high-vigilance conditions, but tends to increase when the participant becomes increasing drowsy in low-vigilance conditions. These results were statistically significant for four of the six study participants.

This limited pilot study observed that one's pain threshold may or may not initially decrease as originally hypothesized depending on the participant, but then increases as one becomes drowsier. While not definitive, the methods and results of this study may help to refine our hypotheses and design future studies in pursuit of detector-free on-demand driver vigilance enhancement that exploits our body's endogenous alert mechanism.