Citation

Youngblood WP, Woltman HL. Transp. Res. Rec. 1978; 681: 20-24.

Copyright

(Copyright © 1978, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Recommendations related to nighttime luminance for traffic signing are not readily translatable from specification or photometric descriptions of the reflective brightness of materials. An investigation of a simple means of translation was undertaken to aid in the proper selection and application of materials where a sign luminance level is desired. The study approach used a photometric determination of specific intensity of the reflective material. The two observation angles common to most highway specifications, 0.2 deg and 0.5 deg at -4 deg entrance angle, were used for determining a broad luminance span for a variety of reflective materials in the common traffic colors. These materials were then installed on a test road where field determinations of sign luminance were also made. The many readings were then correlated by linear regression. These expressions, based on direct observational data, are shown for a variety of shoulder and overhead sign positions, for upper and lower beams, and for the two distances most closely approximating the 0.2 deg and 0.5 deg observation angles--183 and 91.5 m (600 and 300 ft). The resulting experessions permit simple computation of either sign luminance or specific intensity for a reflective sheeting.