To provide the greatest degree of safety for night driving, signs must be adequately retroreflective to ensure proper visibility at night. Additionally, the Federal Highway Administration has established higher minimum retroreflectivity standards that are to be met when signs are replaced.
FHWA requires that all agencies responsible for public roadways implement and use a sign assessment and management method to maintain minimum levels of retroreflectivity by June 13, 2014, and ensure that new minimum retroreflectivity requirements are met when existing signs require replacement.
It is important to consider that even though a particular type of sheeting may initially meet the minimum retroreflectivity levels when it is new (such as Type I and Type II Engineering Grade sign sheeting), it might quickly degrade to below the minimum retroreflectivity levels, thus losing its effectiveness at night and requiring replacement. At a minimum, SDDCTEA recommends the use of Type III sheeting. Even though a higher performance sheeting (Type III minimum) will have a higher initial cost, it will provide a better life-cycle cost. For more information, refer to SDDCTEA's Sign Management Current Practices bulletin, or contact SDDCTEA.