Habituation is what we humans experience when we fail to notice something because our brain believes the information is somewhat unimportant. We roll by a 25 mph (40 km/h) speed limit sign and don’t think too hard about whether we’re actually going below that limit.

 

Wisconsin has a government facility that’s trying to buck that trend with a simple decimal point. Rather than a limit of 15 or 20 mph, drivers have to stay below 17.3 mph (27.8 km/h). And that double-take is exactly the point.