Assessing the visibility of raised pavement markers and alternative forms of delineation

Bullough, John D.; Liu, Xiang · 2020 · DOAJ

DOI: 10.3846/transport.2020.12072

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Summary

This study addresses the need to evaluate the visual effectiveness of Raised Pavement Markers (RPMs) and alternative delineation devices, such as wet reflective pavement tape and barrier-mounted reflective delineators. While RPMs are widely used to improve roadway safety, particularly in wet conditions and complex geometries, transportation agencies are exploring alternatives due to maintenance and cost concerns. The research aims to characterize the luminance and visual performance of these devices under nighttime driving conditions to help agencies determine where specific devices are most beneficial. The researchers conducted laboratory measurements on new RPM samples from three manufacturers (in white, yellow, red, and blue), wet reflective pavement tape, and barrier-mounted reflective delineators. They also tested two used yellow RPMs to assess performance degradation. Using a handheld luminance meter and a light source simulating low-beam headlights, they measured luminance across various geometric conditions, including vertical angles from straight ahead to 1° down and horizontal angles from 10° left to 10° right. These measurements were used to calculate the coefficient of retroreflectivity and estimate roadway scenario luminances at a distance of 100 m. The study then applied the Relative Visual Performance (RVP) model, which accounts for luminance, contrast, target size, and observer age (assumed to be 60 years), to estimate driver visual performance. The results indicated that while there were large variations in the luminance of the devices (ranging from 16.42 to 389.35 cd/m²), the resulting RVP values at a 100 m viewing distance were relatively small (0.995 to 1.029). This insensitivity is attributed to the "plateau" characteristic of visual performance, where increases in luminance beyond a certain point yield diminishing returns in visual speed and accuracy. Consequently, all devices were found to be highly visible from 100 m away. However, differences became apparent when analyzing threshold visibility distances, which ranged from approximately 150 to 400 m. Used RPMs exhibited luminances 20–30% lower than new RPMs but maintained similar visibility characteristics. The analysis demonstrated that as viewing distance increases, visibility decreases due to the inverse square law of illumination and the reduction in the apparent angular size of the target. The significance of this work lies in providing a method for practitioners to characterize the visual effectiveness of RPMs and alternative delineation systems. By linking photometric measurements to visual performance models, the study offers a tool to identify when and where specific devices contribute most to driving safety. The findings suggest that while many devices perform similarly at close ranges, their threshold visibility distances vary significantly, which is critical for maintaining lane position and vehicle speed on curves or in low-visibility conditions. This approach allows for more informed decision-making regarding the selection and placement of roadway delineation devices.

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

Topics

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• emergency work zone conspicuity
• vehicle conspicuity
• signage environment
• visibility analysis litigation
• sign visibility legibility
• perceptual countermeasures