The development of minimum retroreflectivity (MR) levels for traffic signs has been going on for more than two decades, but it was significantly accelerated in 1984 when the Center for Auto Safety petitioned the Federal Highway Administration (FHWA) to establish retroreflectivity standards. During the past decade, several sets of recommended MR levels for traffic signs have been proposed. However, these preliminary recommendations have been based on a headlamp-beam pattern that represents vehicle design from the mid- to late-1980s. Vehicle headlamps have changed significantly since then. Other significant changes also have prompted the need to update the recommended MR levels for traffic signs before FHWA initiates the rule-making process. This report includes an updated set of recommended MR levels for traffic signs based on recent developments in vehicle headlamps, vehicle types/sizes, night-time driver needs, and newer sheeting materials. The updated MR levels are also based on more robust computer modelling of retroreflective sheeting performance. (Author/publisher)
Abstract