Visibility Requirements for Traffic Control Devices in Work Zones

The objective of this study was to develop a performance requirement or standard for the detection and recognition of retroreflective traffic devices used in work zones. The scope of the study was limited to an analytical exercise and drew on existing information and data where possible. The discussion focuses primarily on those channelization devices frequently used in work zones (i.e., drums, barricades, panels, and cones). The performance standard developed in this study was established from the principles of driver information needs and, specifically, the requirement for decision sight distance. The performance standard is presented in terms of visibility requirements, that is, the distance at which motorists should be able to detect and recognize the devices at night. The standard selected was a minimum distance of 275 m (900 ft) when illuminated by the low beams of standard automobile headlights at night under normal atmospheric conditions. This appears to be a reasonable, allbeit arbitrary, standard which should cover most situations.