Citation

Harrington TL, Johnson MRD. Highw. Res. Board bull. 1962; 336: 111-113.

Copyright

(Copyright © 1962, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

A photocell detector is described which is color-corrected to cie standard observer response, maintaining instrument resolution at 0.1 degrees with direct meter reading eliminating subjective effects. Ambient daylight effects are minimized by use of source light interrupted at a frequency also required for detection. Power is supplied by rechargeable dry cells, permitting convenient portability. Extensive measurements of various retro- reflective materials on both concrete and bituminous pavements have been conducted, and yield reproducible results highly consistent with visual experience. Measurement of efficient reflective materials is now possible along with increased sensitivity in measurement of reflective marking paints.