No doubt about it, digital signage is the major trend in sign technology, worldwide.
Many cities are grappling with the policy issue of whether, or to what degree, they should allow digital signs. Such signs are known by various names, including "electronic signs," "electronic readerboards," "electronic message centers," "changeable electronic variable message signs," and more. Regardless of name, digital signs allow the image on the sign to be changed frequently, usually by remote control. Most digital signs are capable of full motion video, which is allowed in some intense entertainment areas, such as the Las Vegas Strip or Times Square NYC. But most digital signs display a sequence of still images, "slide show" style. The time that each image is on display is called "dwell time" or "hold time." Cities that allow digital signs often set rules about hold times, time of transition between images, and brightness of the screen. Sometimes digital conversion of existing billboard is allowed in exchange for the billboard company removing a certain number of older signs, typically those near residential neighborhoods or other sensitive areas. So far, there does not seem to be a "standard number" for the exchange rate.
Digital signs often present a serious policy question for local governments. Business, commercial and advertising interests insist that they must be allowed to compete with the most modern technology. Scenic and environmental interests counter that digital signs are garish, glaring, and that they cheapen and carnivalize the city's public viewscapes, and cause much more driver distraction.
Only a few court cases have involved digital sign policies. So far all the cases hold that a ban on digital signs is not unconstitutional.
Two of the cases arose out of the same city, Concord NH. Naser Jewelers v. Concord was decided in the U.S. Court of Appeal for the First Circuit. The court's decision is available here:
A highly similar case, Carlson's Chrysler v. Concord, was decided by the NH Supreme Court. It also validated the "no electronic message centers" rule. Read that decision here: