Glare Screen Guidelines

TRB's National Cooperative Highway Research Program (NCHRP) Synthesis 66: Glare Screen Guidelines will be of interest to design engineers and others seeking information on the use of glare screen to shield drivers' eyes from the headlights of oncoming vehicles. Information is presented on various types of glare screen and the parameters involved in their design. Glare can be avoided through highway design (wide medians, separate alignment, earth mounds), barriers, plantings, fencing, or glare screen on median barriers. Glare screen may be continuous partition (either opaque or with intermittent openings or a series of objects of such width and spacing as to block out glare. Design parameters for glare screen include median width, barrier type, vertical curvature, and horizontal curvature. Among the conclusions of the synthesis are: accepted cutoff angle for glare screens is 20 degrees plus the degree of curvature; more effort is needed to simplify glare screen hardware for easier maintenance, development of an accident warrant is not likely; veiling brightness should be studied to see if it can be used as a warrant for glare screen; and geometric design standards should be reviewed in relation to use of glare screens in median.