How are Drivers' Stress Levels and Emotions Associated with the Driving Context? A Naturalistic Study

Abstract

Understanding and mitigating drivers' negative emotions, stress levels, and anxiety is of high importance for decreasing accident rates, enhancing road safety, and providing a healthy lifestyle to the community of drivers. While detecting drivers' stress and negative emotions can significantly help with this goal, understanding what might be associated with increases in drivers' negative emotions and high stress level, might better help with planning interventions. While studies have provided significant insight into detecting drivers' emotions and stress levels; not many studies focused on the reasons behind changes in stress levels and negative emotions. In this study, by using a naturalistic driving study database, we analyze the changes in the driving scene, including road objects and the dynamical relationship between the ego vehicle and the lead vehicle with respect to changes in drivers' psychophysiological metrics (i.e., heart rate (HR) and facial expressions). We find that different road objects might be associated with varying levels of increase in drivers' HR as well as different proportions of negative facial emotions detected through computer vision. Our results indicate that larger vehicles on the road, such as trucks and buses, are associated with the highest amount of increase in drivers' HR as well as negative emotions. Additionally, we provide evidence that shorter distances to the lead vehicle in naturalistic driving, as well as the higher standard deviation in the distance, might be associated with a higher number of abrupt increases in drivers' HR, depicting a possible increase in stress level. Lastly, our results indicate more positive emotions, lower facial engagement, and a lower abrupt increase in HR at a higher speed of driving, which often happens in highway driving. Our results collectively show that driving at higher speeds happening in highways by avoiding certain road objects might be a better fit for keeping drivers in a calmer, more positive state. This research lays the ground for designing human-centered vehicles, urban environments, and services that can understand the level to which each road object and environment might affect drivers' and passengers' wellbeing.

Investigating Cardiovascular Activation of Young Adults in Routine Driving

“…Our study has three elements that make it stand out from other naturalistic driving studies [18], [22]. First, we systematically capture behavioral cycles at the weekly and daily levels, by shadowing participants for a full week, day and night, without any interruption.…”

“…We lock on a week as a monitoring period, because we consider it as standard cycle of human behavior. In other naturalistic driving studies, researchers do not collect non-driving data from participants; even their driving data are collected opportunistically, that is, driving data do not come from consecutive days of a specific week [22] Analysis of Sustained vs. Event Based Behaviors.…”

“…We also consider the video channel very intrusive and privacy-compromising, without bringing unique and essential information for our physiological outcomes study. In naturalistic driving studies, dual video, from cameras looking inside and outside, brings three pieces of information by the way of computer vision methods [18], [22]: a) drivers' apparent emotional valence through recognition of facial expressions; b) assessment of distractions (e.g., texting) through activity recognition; and, c) a measure of outside traffic through vehicle detection in the dash camera's field of view. We do not have access to STUDY VARIABLES NUBI Drive HARMONY [18] 100-Driver Study [23] SHRP-2 [13] Study…”

“…Larger vehicles on the road, such as trucks, are associated with the highest amount of increase in drivers' heart rate as well as negative emotions. Additionally, shorter distances and higher standard deviation in the distance to the lead vehicle are associated with a higher number of abrupt increases in drivers' heart rate, indicating a possible stress increase [22].…”