10-13-05 Planning Comm. Agenda - Laserfiche WebLink

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Message Signs." This report was an exhaustive analysis of the safety implications of EMDs used along highways. The report highlights the inconclusive nature of safety studies that had occurred to that time, some concluding that roadside signs posed a traffic distraction, and others concluding that roadside signs do not cause traffic accidents. In view of the inevitable use of the technology in signage, the report made some sensible observations about traffic safety considerations for such signs: 1. Longitudinal location. The report recommended that spacing standards be adopted to avoid overloading the driver's information processing capability. Unlike the standard for sign regulations in 1980, most communities today have spacing standards already integrated into their sign codes. 2. Lateral location. Often referred to as "setback," the report initially recommended the common sense requirement that such signs be placed where the risk of colliding into the sign is eliminated. This was a legitimate concern, as such signs were being contemplated for use by highway departments themselves in the right-of-way. Private use of roadside signs is generally limited to locations outside the right-of-way, so this should not be a significant concern. The next issue addressed by the report was visibility. The report advocated the minimum setback feasible, stating that "standards for lateral location should reduce the time that drivers' attention is diverted from road and traffic conditions. Generally this suggests that signs should be located and angled so as to reduce the need for a driver to turn his head to read them as he approaches and passes them." This can best be handled by permitting such signs to be located at the properly line, with no setback, and angled for view by oncoming traffic. 3. Operations: Duration of message on-time. The report states that the duration of the message on-time should be related to the length of the message, or in the case of messages displayed sequentially, the message element. For instance, based on state highway agency experience, comprehension of a message displayed on a panel of three lines having a maximum of 20 characters per line is best when the on-time is 15 seconds. In contrast, the customary practice of signing which merely displays time and temperature is to have shorter on-times of 3 to 4 seconds." Since this 1980 report, state highway agencies have adopted, for use on their own signs, informal standards of considerably shorter "on" time duration, with no apparent adverse effects on traffic safety. Federal legislation affecting billboard use of electronic signs- ------------ 25-