The signals have been developed by Taro Ochiai, a professor at Kyushu Sangyo University, with the first set of traffic lights installed in the southern city of Fukuoka. A second month-long test is to be started in Tokyo before the end of February.
Prof Ochiai began researching the use of light-emitting diodes in 2003, when they first began to be used in traffic lights in preference to regular light bulbs. Drivers with colour-blindness quickly reported that the LED signals were more difficult for them to discern based only on brightness as the visual indicator.
Working with lighting manufacturer Koito Electric Industries Ltd., Prof Ochiai incorporated blue LEDs with four times the brightness of the other diodes in the shape of a cross through the red lamp.
Read the rest of the story: Japan testing traffic lights for colour-blind drivers.