Most of us have grown up recognizing the classic red octagonal stop sign as an unmistakable symbol of caution and order on the road. So, when a blue stop sign appears, it can be both puzzling and ...

If there’s one rule of the road we learn long before driver’s ed, it’s this: Red means stop. Even a toddler can tell you the right shade of a stop sign. Since roughly the 1950s, all government-issued ...