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

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change interval or "off-time' between messages. The message changes on sequential segmented messages should be displayed such that a motorist can see and read the entire chain of message segments in a single pass. Messages should be permitted to change at "reasonable intervals." Such signs should have adequate spacing between signs, but be set back from the right- of-way as little as feasible. Since 1980, no new information has become available supporting a traffic safety concern about EMDs. They have been installed in highway locations, along city streets and in urban core settings, using all forms of operations: static, sequential messaging and full animation. Despite such widespread use, and the presence of environmental organizations generally adverse to sign displays, no credible studies have established a correlation between EMDs and a degradation in traffic safety. An article in the Journal of Public Policy and Marketing in Spring, 1997, arrived at the same conclusion. Professor Taylor, of Villanova University, analyzing this lack of data to support such a correlation, concluded that "there appears to be no reason to believe that changeable message signs represent a safety hazard." From a safety standpoint, and based on the studies and practical experience that has been accumulated since the widespread use of EMDs, some conclusions can be reached: • In an urban core setting, where a sense of visual vitality and excitement is desirable, full-animation EMDs have been shown to be viable without degrading traffic safety. • n an urban setting, such as along arterial streets, EMDs have been use ' with static messages changed by use of transitions such as traveling, ~'~ scrolling, fading and dissolving, without any apparent impact on traffic safety. Quite likely, this can be attributed to the primacy of the navigation task, and the secondary nature of roadside signage. r • on n er imit~ess highways, the only significant traffic safety analysis recommends the use of static messages only, and the federal government permits message changes at "reasonable intervals." Many highway departments change messages on their own signs every 1-2 seconds. The report further recommends that sequential messages be timed to ensure that the entire sequence of messages be displayed in the time it takes a car to travel from initial legibility to beyond the sign. In practice, and in the 20+ years since publication of this report, the operational characteristics of such signs have been expanded to include 28- ~