Criminals, including those convicted of minor offenses, were given green triangles. Jewish people were given yellow triangles arranged to form the Star of David.

There are a few reasons why the colors red, yellow, and green were chosen for traffic lights. Red is an obvious choice. The color red means danger or to be alert for something occurring.

Henry Liu, a civil engineering professor who is leading a study through the University of Michigan, said the rollout of a new traffic signal system could be a lot closer than people realize.

Eventually, the upgrades could do away entirely with the red, yellow and green lights of today, ceding control to driverless cars. Henry Liu, ...

Eventually, the upgrades could do away entirely with the red, yellow and green lights of today, ceding control to driverless cars. Henry Liu, ...