Service life of retroreflective traffic signs

Abstract

The ability to predict coefficient of retroreflection (RA) values for inservice traffic signs is critical for the Federal Highway Administration's (FHWA) Sign Management System (SMS). Within the SMS, tools for predicting inservice retroreflective performance of traffic signs and for determining the motorist's visual needs are required. The research which focuses on the motorist's needs in terms of traffic sign luminance, legibility distance, conspicuity, etc., is on-going by others. The project reported on here evaluated the effects of climatological and geographic variables on sign sheeting deterioration. A national data collection effort was undertaken. Data samples from 6,275 traffic signs were collected across the country. The data collected included; sheeting retroreflectivity, ground elevation, orientation to the sun, date of installation, sheeting type, etc. Mathematical equations were developed using the key deterioration variables to predict inservice coefficient of retroreflectivity (RA) and legend to background contrast ratios. The main difficulty in modeling sheeting deterioration was the result of the variation in the coefficient of retroreflectivity for new sheeting.