Why the lights don't use a single lamp to change color and light

Manufacturer of light road traffic lights are all very familiar with, in the impression of people are generally three color lights. Recently a friend asking, why road traffic signal light planning into three lights, and don't use a lamp to change color way?

light manufacturers of road traffic signal lamp is everyone are very familiar with, in each person's impression is generally three color lights. Recently, a friend asked, why there are three lights road traffic lights club plans, rather than a lamp to change color? In the middle of the 19th century, light is the first to show the UK and other European countries road traffic lights. At that time, only two lights are red and green. Later, it developed into three lights or four lights ( Two lights for go straight and turn) 。 On the one hand, due to technical reasons, but also for real time a lamp switch different colors. Fixed arrangement of multiple lights, on the other hand, also can take care of color blind people, help them to identify. At present, many traffic lights using led lattice skills ( Light emitting diode) 。 A single light of color conversion no threshold. Some people also invented a single traffic lights, it also shows different graphics to help identify color blindness. However, the main reason is the color of the light emitting diode lamp switch are not yet common. Internal current was a controller to increase or decrease. When the applied voltage is key, display colors may lead to failure. The traffic lights in this area for very accurate, must be able to resist ultraviolet light. Therefore, the safest thing is still set the current three lights. Road traffic signals, in short, do not use a lamp to change color, on the one hand is due to the technology co. , LTD. As these lights used for so many years, they now have become a part of the people are used to, so there is no need to make any changes. On the other hand, it can better help color-blind people identify.