Visibility Requirements of Work Zone Traffic Control Devices

A concern among highway safety officials is that traffic control devices used at work zones are not as visible as they should be due to insufficient reflectance properties or because they have become so dirty as to render them ineffective. To overcome this deficiency, it has been suggested that a performance standard be established for reflective devices used in work zones. Accordingly, the contractual objective of this study was to develop a performance requirement or standard for the detection and recognition of retro-reflective traffic devices used in work zones. The performance standards developed in this study are established from the principles of driver information needs and, specifically, the requirement for decision sight distance. Furthermore, they are 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 scope of the study was limited to an analytical exercise, drawing on existing information and data, where possible. The discussion focuses primarily on those channelization devices frequently used in work zones, i.e., drums, barricades, and panels. Also included is a recommended program of research which would validate the findings of this study and address several issues related to reflectivity and driver visibility needs.