TRAFFIC LIGHTS RED,YELLOW AND GREEN

Red means stop and green means go has impacted our lives in move ways than traffics signals.
                                                                                                                                                 

                  The color red means danger which has been taught from a young age and green means its okay to move forward.Why were those particular colors chosen for traffics lights in the first place?
                                                                                                                                                                        Its important to know that traffics lights for cars become thing were traffics signals for train.At first         rail road companies used red to mean stop,white mean go and green to mean caution.                                                                                                                                                                                              Train condition ran into a few problem with white meaning go.Red goes,that always been a color         with the longest wavelength so it can be seen from greater distance than other colors.Yellow goes,it was used to caution drivers because it has slightly wavelength than red,not short as green.  
                     
           Yellow was once used to stop ,at least as far as signage goes.Some stop signs were yellow because it was to hand to see red sign in a poorly lit area.Materials were developed that were highly reflective of the day school zones,some traffics signs and schools buses continue to be painted yellow.