# Efficacy of Fragrance Types and Intervention Methods in Reducing Driver Fatigue and Modulating Emotional Development Assessed by HRV and Subjective Indicators

## TL;DR

This study shows that in-vehicle fragrance, especially when continuously released, can reduce driver fatigue and improve emotions, based on heart rate and self-reports.

## Contribution

The study systematically compares fragrance types and release methods for their effects on driver fatigue and emotions using HRV and subjective measures.

## Key findings

- Fragrance intervention significantly reduced subjective fatigue ratings compared to no intervention.
- Continuous fragrance release showed the most pronounced reduction in fatigue and improved HRV.
- Fragrance type had limited impact, suggesting release mode is more important than fragrance type.

## Abstract

Driver fatigue and negative emotions are significant factors contributing to traffic accidents. In-vehicle fragrance, as a fatigue intervention strategy, can help improve drivers’ mental and emotional states, preventing accidents. However, there is a lack of systematic research on how different fragrance types and release methods affect drivers’ fatigue and emotional development. Forty healthy drivers (mean age: 31 years, gender balanced) participated in this study. Participants were randomly assigned to two groups: one group tested three different fragrance types (HINOKI, GRASSY, YUZU), and the other group tested three fragrance release methods (CR: continuous release, IR: intermittent release, and PR: pulse release). All participants completed a simulated driving task under specified in-vehicle fragrance management conditions. Subjective fatigue ratings and emotional self-assessments (POMS) were used to assess changes in fatigue and emotions, and heart rate variability (HRV) was measured to evaluate physiological changes. Compared to no intervention, fragrance intervention significantly reduced drivers’ subjective fatigue ratings, with the continuous release mode showing a more pronounced reduction in fatigue scores. Fragrance intervention effectively improved heart rate variability, with significant differences observed between release modes. The fragrance intervention also had a significant effect on emotional ratings, notably increasing vigor and reducing negative emotions such as tension and anxiety. The impact of fragrance type on fatigue scores, HRV, and emotional ratings was limited, suggesting that the effectiveness of fragrance intervention may depend more on the intensity and release mode of the intervention rather than the fragrance type. Fragrance intervention effectively reduces driver fatigue and improves emotional states, with the continuous release mode showing the most significant effects. The findings of this study can provide valuable insights for customizing in-vehicle fragrance release strategies to alleviate fatigue and improve emotional well-being in individuals engaged in long-duration driving tasks, with significant implications for the management of drivers’ mental and psychological health.