Investigating the effectiveness of perceptual treatments on a crest vertical curve: A driving simulator study
DOI: 10.1016/j.trf.2018.06.002
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Summary
This study investigates the effectiveness of low-cost perceptual treatments in reducing driving speeds on a crest vertical curve, a critical road geometry often associated with high crash rates due to limited visibility and speeding. While perceptual measures like transverse bars have been studied for intersections and horizontal curves, there is a lack of data regarding their application on crest vertical curves. The research aims to identify the most effective pavement marking pattern to mitigate speed-related risks before field implementation, utilizing a driving simulator to compare three specific treatments against a baseline condition. The experiment was conducted using a validated fixed-based driving simulator at Roma Tre University. The simulated scenario replicated a two-lane rural road near Rome, Italy, featuring a crest vertical curve with reduced stopping sight distance. Forty-four volunteers participated, though the final analysis included 38 drivers after excluding outliers and those experiencing simulator sickness. Participants drove four conditions: a baseline (no treatment), white peripheral transverse bars, red peripheral transverse bars, and optical speed bars. The peripheral bars used an exponential spacing design to create an optical illusion of acceleration, while optical speed bars consisted of widening bars with decreasing spacing. Data collection involved recording speeds at six points along the curve and administering a questionnaire to assess subjective risk perception, desired speed, and treatment comprehension. Field speed measurements were also taken to validate the simulator’s accuracy. The results confirmed the simulator’s validity, as simulated speeds were not statistically different from field measurements. Regarding effectiveness, only the red peripheral transverse bars significantly reduced driving speeds, achieving an average reduction of 6 km/h compared to the baseline. White peripheral transverse bars and optical speed bars did not yield statistically significant speed reductions. Subjective questionnaire data highlighted discrepancies between drivers’ static evaluations and their actual driving behavior, underscoring the importance of dynamic simulation over static image assessment. The study found that while all treatments were intended to increase perceived risk, only the red markings successfully translated this perception into measurable speed reduction. The significance of this research lies in its demonstration that driving simulators are effective tools for pinpointing specific speed-reducing measures and selecting the most efficient ones prior to costly field implementation. The findings suggest that color plays a crucial role in the efficacy of peripheral transverse bars, with red markings outperforming standard white ones. This contributes to the literature by providing evidence-based recommendations for road safety engineering, specifically advocating for the use of red peripheral transverse bars on crest vertical curves to enhance driver safety and reduce crash potential.
Key finding
Red peripheral transverse bars were the only perceptual treatment tested that significantly reduced driving speeds on a crest vertical curve.
Methodology
simulator
Sample size: 38
Provenance
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| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | Crossref | — | — | 1 | 2026-06-05 |
| archive | success | canonical_url | — | — | 1 | 2026-06-06 |
| extract | success | cached | — | — | 3 | 2026-06-10 |
| clean | success | clean | — | — | 1 | 2026-06-07 |
| chunk | success | chunk | — | — | 1 | 2026-06-07 |
| embed | success | embed | Qwen/Qwen3-Embedding-8B | — | 1 | 2026-06-07 |
| enrich | success | semantic_scholar | — | — | 1 | 2026-06-06 |
| promote | success | — | — | — | 1 | 2026-06-05 |
| 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.
Topics
Ranked by relevance to this paper. Hover a topic for its definition.
- perceptual countermeasures
- road geometry
- rail grade crossings
- speed distance perception
- speed choice
- speed management
Information type
What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).
- Applied Guidance: countermeasure evaluation
- Methodological Resource: tool software, validation psychometrics