@article{ref1,
title="Relation between sign luminance and specific intensity of reflective materials",
journal="Transportation research record",
year="1978",
author="Youngblood, W. P. and Woltman, H. L.",
volume="681",
number="",
pages="20-24",
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.<p />",
language="en",
issn="0361-1981",
doi="",
url="http://dx.doi.org/"
}