07-12-07 Planning Comm. Agenda - Laserfiche WebLink

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Meeting of June 14, 2007 Page 6 Subject: Dynamic Signs If dynamic signs become pervasive and there are no meaningful limitations on each sign's ability to change frequently, drivers may be subjected to an unsafe degree of distraction and sensory overload. Accordingly, a longer display time is appropriate. The ordinance establishes a minimum display time of 20 minutes, which is the standard adopted by the city of Bloomington following its own thorough study. This is less than the one-hour display time that is currently in effect through the district court's temporary injunction, and thus provides greater flexibility to sign owners. There would be an exception for time and temperature signs, which the federal court has recognized as a legitimate exception to limitations on variable message signs. The ordinance provides that a display of time, date, or temperature must remain for at least 20 minutes before changing to a different display, but the time, date, or temperature information itself may change no more often than once every three seconds. The ordinance provides that each sign must be designed to freeze the device in one position if a malfunction occurs. The displays must also be equipped with a means to immediately discontinue the display if it malfunctions, and the sign owner must immediately stop the dynamic display when notified by the city that it is not complying with the standards of this ordinance. Brightness Levels The consultants determined that the brightness of signs can be distracting, and if very bright, can actually result in a "blinding" effect, particularly at night. Pure white light appears the most bright, and has the most blinding capability. Unfortunately, there is currently no good way to measure the brightness of signs in the field. Sign manufacturers can measure the light emitted by LED signs in a controlled factory setting by measuring the "nit" level, but those conditions cannot be re-created in actual field conditions. Additionally, the instruments used to measure brightness are currently very expensive. With no good way of measuring brightness, the ordinance incorporates the general standard adopted by the Wisconsin Department of Transportation: "No [sign] may be illuminated to a degree of brightness that is greater than necessary for adequate visibility." The general philosophy is that dynamic signs should have the same appearance as regular signs both during the day and at night. Additionally, the ordinance contains two other general standards found in Indiana and Ohio regulations, which provide: No sign may be of such intensity or brilliance as to impair the vision of a motor vehicle driver with average eyesight or to otherwise interfere with the driver's operation of a motor vehicle. 6-