Ahtanum Valley Museum

Familiarity with traffic signs generally means we simply no longer pay much heed to them. They become part of the background like trees or light poles and don't draw our attention in the same way after a bit. This, in part, is probably responsible for the quantity of cars that speed thru an area at any particular time—the drivers are so familiar with the place, they go whatever speed seems reasonable instead of remembering to follow the signs.

Familiar Traffic Signs are Necessary

Given that a sign loses its efficacy over time it'd appear counter-productive to choose dynamic signs that are similar to static signs. If familiarity is an element of the difficulty, you might be pondering why lit and dynamic signs aren't made differently. Why not use a totally new design that drivers are not used to to get their interest even more? Why don't you try a large star-shaped sign, or one in a new, unused colour to make certain that drivers don't see the signs as an element of the background?

Familiar Speed Signs Instruct Drivers

The answer is a simple one—the signs need to look "real." The familiarity of the signs we are used to mixed with the changing display is generally enough of a difference to get drivers ' attention, and it appears to be familiar enough to make drivers take the signs seriously.

The changing display that responds to each driver's speed is sufficient to draw drivers' attention, give them feedback that is immediately processed and answered to, and slow drivers down. This, within the familiar context of the standard speed limit sign, offers enough difference and personalized feedback to create a change in the driver's behavior, while being familiar enough for a driver to accept the sign as something he or she needs to pay heed to.

A new design or colour could seem false or unlicensed and be ignored. That would just make the sign ineffectual. A worst case scenario would have the sign causing perplexity in some drivers, which could cause traffic issues.