Photometric Requirements for Portable Changeable Message Signs

Portable changeable message signs (PCMSs) are traffic control devices that advise motorists of unexpected traffic and routing situations. In contrast to static signing, PCMSs convey dynamic information in a variety of applications, such as work zones, incident management, traffic management, and warning of adverse conditions. Although PCMSs have been used in traffic control applications for many years, there are no established photometric standards for the device that can be used as the basis for a procurement specification. The only provision related to the visibility of PCMSs is a requirement in the Texas Manual on Uniform Traffic Control Devices for Streets and Highways – Part VI which indicates that PCMSs be visible from at least a half mile (under ideal day and night conditions) and the sign message be legible at a minimum of 650 ft. However, the manual does not provide a means for determining whether PCMSs meet these criteria.
This project reviewed the performance of PCMSs and developed photometric standards to establish performance requirements. In addition, researchers developed photometric test methods and recommended them for use in evaluating the performance of PCMSs. This report includes a review of the literature and provides documentation for the standards and procedures recommended.