Operational Effects of Wide Edge Lines Applied to Horizontal Curves on Two-Lane Rural Highways

Donnell, Eric T.; Gemar, Mason D.; Donnell, Eric T. · 2006 · ROSA P / Pennsylvania State University. The Pennsylvania Transportation Institute

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Summary

This study evaluates the operational effects of applying wide (8-inch) edge lines to horizontal curves on two-lane rural highways in Pennsylvania. While standard edge lines are 4 inches wide, wider lines are hypothesized to provide greater emphasis and improved guidance for motorists, particularly at night. The research was motivated by the need to determine if wider edge lines improve driver behavior and safety on curves, as existing warrants for pavement markings are based primarily on traffic volume rather than safety or operational performance. Due to insufficient crash data during the study period, the researchers focused on quantifiable surrogate measures of safety, including vehicle speed, lateral position, and encroachment frequency. The study employed a before-after observational design with comparison sites to isolate the effects of the treatment. Four treatment sites with wide edge lines were paired with four geometrically similar comparison sites with standard 4-inch edge lines. Data were collected using piezoelectric sensors to measure vehicle speed and lateral position at both the approach tangent and the midpoint of the horizontal curves. The analysis considered both daytime and nighttime conditions and accounted for the presence of opposing traffic. Performance metrics included mean speed, speed variance, mean lateral vehicle position, lateral position variance, and the proportion of vehicles encroaching onto the shoulder or opposing lane. Statistical methods, including Anderson-Darling normality tests and differential analysis between tangent and curve sections, were used to assess changes in driver behavior. The results indicate that wide edge lines do not consistently alter driver behavior patterns regarding speed or lateral vehicle position. There were no significant, consistent changes in mean speed, speed variance, or lateral position variance attributable to the wider markings. Similarly, the proportion of vehicle encroachments along the curves did not show a consistent change. However, a subjective assessment of speed profile plots revealed that drivers tended to begin decelerating earlier when approaching curves with wide edge lines at night compared to those with standard lines. This suggests that wide edge lines may improve the visibility of the curve geometry, allowing drivers to recognize the need to slow down from a greater distance during nighttime conditions. The significance of these findings lies in the nuanced understanding of how pavement marking width affects driver perception versus operational control. While wide edge lines did not produce measurable improvements in speed consistency or lane positioning, the evidence of earlier speed reduction at night implies enhanced curve delineation. This supports the potential utility of wide edge lines as a safety countermeasure for improving driver awareness of horizontal curves in low-light conditions, even if they do not necessarily constrain lateral vehicle placement or reduce encroachment rates. The study provides empirical data to guide transportation agencies in the application of wider edge lines, highlighting their specific benefit for nighttime curve recognition rather than general operational control.

Key finding

Wide edge lines applied to horizontal curves on two-lane rural highways do not consistently change encroachment proportions or driver behavior patterns, but they enable drivers to recognize curves at night from a greater distance.

Methodology

field_study

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 (6 acquisition events logged).

Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

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• perceptual countermeasures
• road geometry
• roadway lighting effects
• lane positioning

Information type

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• Empirical Findings: crash risk outcomes