PHYSIOPSYCHOLOGICAL RESPONSE OF VEHICLE PASSENGERS TO SURFACE ROUGHNESS AND THE ACCEPTABLE LIMIT
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Summary
This study investigates the physiopsychological responses of vehicle passengers to road surface roughness, aiming to establish an acceptable limit for the International Roughness Index (IRI) that ensures both comfort and safety. The research addresses the need to evaluate road profiles based on human response rather than solely physical characteristics, linking surface roughness to cognitive performance and mental stress. The experimental design utilized a driving simulator with 24 participants (12 men and 12 women, average age 21.6 years). Participants were exposed to three levels of surface roughness, defined by IRI values of 0.9, 5.3, and 10.5 mm/m, while traveling at 60 km/h. The study measured two primary indicators: perceptional reaction time, assessed via a voice key response to visual stimuli to gauge psychological attentional resources, and heart rate variability (HRV) indices to measure physiological stress. Specifically, the high-frequency (HF) component of HRV was used to indicate short-term mental stress, while the ratio of low-frequency to high-frequency power (LF/HF) indicated long-term mental stress and autonomic nervous system balance. The results demonstrated a significant correlation between increased surface roughness and degraded human performance. Perceptional reaction times increased significantly as IRI values rose, indicating a reduction in cognitive performance and safety potential. Physiologically, both short-term stress (HF) and long-term stress (LF/HF) increased proportionally with higher IRI values. Statistical analysis confirmed that reaction times and HRV indices were significantly different across the roughness levels, with the highest stress and slowest reactions observed at the 10.5 mm/m IRI level. The study further validated these findings by comparing them with previous research using different roughness evaluation methods, confirming that higher roughness leads to increased mental fatigue and slower reaction times. Based on these findings, the study identifies an acceptable IRI limit of 5.4 mm/m for highways. This threshold is derived from the point where significant increases in reaction time and mental stress begin to occur. The authors conclude that surface roughness impacts not only ride comfort but also driving safety by increasing mental fatigue and reducing cognitive responsiveness. This provides a quantitative, human-centric standard for road quality evaluation, supporting traditional roughness metrics with physiopsychological evidence.
Key finding
Increasing road surface roughness significantly increases passenger reaction times and mental stress, leading to a proposed acceptable International Roughness Index limit of 5.4 mm/m for highways.
Methodology
simulator
Sample size: 21
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | author_sweep | — | — | 2 | 2026-05-28 |
| archive | success | canonical_url | — | — | 1 | 2026-06-04 |
| extract | success | cached | — | — | 3 | 2026-06-10 |
| clean | success | clean | — | — | 1 | 2026-06-04 |
| chunk | success | chunk | — | — | 1 | 2026-06-04 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-04 |
| enrich | success | — | — | — | 1 | 2026-05-28 |
| promote | success | — | — | — | 1 | 2026-06-04 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 2 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 15 | 2026-06-11 |
| verify | success | — | — | — | 2 | 2026-06-10 |
Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.
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- Empirical Findings: physiological data