Safety Impacts of Using Wider Pavement Markings on Two-Lane Rural Highways in Idaho
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Summary
This study evaluates the safety impacts of wider pavement markings on two-lane rural highways in Idaho, motivated by the high prevalence of single-vehicle crashes caused by drivers failing to maintain lane position. The research employs a multi-method approach, combining observational before-and-after crash analyses, driver simulation experiments, and pavement marking deterioration modeling. The primary objective is to determine if wider longitudinal markings (specifically 6-inch and 8-inch widths compared to the standard 4-inch) improve driver visibility, lane positioning, and overall safety, while also assessing the cost-benefit ratio of such implementations. The methodology involved three distinct components. First, a driver simulator experiment tested 48 licensed participants under daytime and nighttime conditions, varying edge line widths (4-inch and 6-inch) and deterioration levels (0%, 25%, 50%, and 75%). Second, field and laboratory data were used to model the retroreflectivity deterioration of waterborne markings, correlating decay rates with environmental factors like snow load. Third, observational before-and-after studies utilized both comparison group analyses and Empirical Bayes methods to assess crash frequencies and rates on highway segments where wider markings were implemented. The findings indicate that wider pavement markings significantly enhance safety. The Empirical Bayes analysis revealed a 17% reduction in total crash frequency and a 14% reduction in fatal and severe injury crash frequency. Correspondingly, crash rates decreased by 5.53% for total crashes and 12.59% for fatal and severe injury crashes. These reductions are statistically significant at the 90% and 95% confidence levels, respectively. The driver simulation results showed that while wider markings did not significantly alter lane deviation during the day, they produced statistically significant improvements in nighttime driving, where drivers maintained better lane positions as marking deterioration worsened. Additionally, the study found that 6-inch markings degrade more slowly than 4-inch markings, and that retroreflectivity loss is strongly correlated with normalized ground snow load. The significance of this research lies in its strong economic and safety implications for transportation agencies. With an estimated annual cost of $382.05 million for fatal and serious injury run-off-road crashes in Idaho, the implementation of wider markings could yield savings of approximately $48.1 million annually. The study concludes with a cost-to-benefit ratio of approximately 1:25 for implementing wide pavement markings statewide. These results support the adoption of wider edge lines as a effective countermeasure for reducing severe crashes, particularly on rural highways where visibility and lane delineation are critical.
Key finding
Wider 6-inch edge-line pavement markings on Idaho rural two-lane highways reduced total crashes 17% and fatal/severe-injury crashes 14% in Empirical Bayes before-after analysis, with statistically significant crash-rate reductions and an estimated 1:25 implementation cost–benefit ratio.
Methodology
mixed_methods
Sample size: 48 licensed simulator participants; 38 treated highway segments (175.39 mi) vs control segments (168 mi)
Provenance
The full processing record for this entry. Every stage of this paper's journey through the pipeline is logged — what ran, with which tool and model, how many attempts it took, and when it last completed. Discovered via bulk_ingest_rosap on 2026-05-23 (5 acquisition events logged).
| Stage | Outcome | Tool | Model | Prompt | Attempts | Completed |
|---|---|---|---|---|---|---|
| discover | success | rosap | — | — | 2 | 2026-05-23 |
| archive | success | — | — | — | 1 | 2026-05-23 |
| extract | success | cached | — | — | 2 | 2026-06-10 |
| clean | success | — | — | — | 1 | 2026-06-01 |
| chunk | success | — | — | — | 1 | 2026-06-01 |
| embed | success | — | — | — | 1 | 2026-06-02 |
| enrich | success | — | — | — | 1 | 2026-05-23 |
| promote | success | — | — | — | 1 | 2026-05-23 |
| summarize | success | llm | qwen3.6-27b-prismaquant | summ-v5 | 2 | 2026-06-10 |
| tag | success | vector_similarity | — | — | 24 | 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: crash risk outcomes