Experimental Determination of Glass Bead Retroreflectivity for Aircraft Geometries
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Authors
Sloan, Joel
Butler, Samuel
Ullom, Jessica
Wander, Joseph
Issue Date
2019-07
Type
Other
Language
en_US
Keywords
Alternative Title
Abstract
Spherical glass beads embedded within paint aid in visibility of pavement markings at night. Retroreflectivity measurements on roadways are based on ASTM E1710, a standard using parameters for an automobile 30 meters from the point of interest on the pavement. Various manufacturers’ equipment replicate this geometry and conveniently conduct measurements on pavement markings. However, aircraft geometry varies widely, and entrance and observation angles differ significantly from those of a passenger car. Literature suggests that the higher refractive index of Type III beads (1.9) over Type I beads (1.5) provides a higher peak reflectance but returns light at a narrower range of angles than Type I. A complete angle scatter instrument measured the bidirectional reflectance distribution function of beads of both types embedded in white paint. Results are reported for angles more appropriate for large-aircraft geometries. Limited results from this study confirm the higher retroreflective peak of Type III beads, but also suggest that Type I may beads provide marginally higher retroreflectivity for large aircraft with observation angles exceeding ±7°, as encountered during taxiing.
Description
Citation
Sloan, Joel & Butler, Samuel & Ullom, Jessica & Wander, Joseph. (2019). Airfield Pavement Performance Evaluation. 436-446. 10.1061/9780784482476.043.
Publisher
ASCE