Pot Black

Japan is road testing new traffic lights that can be seen by people who are colour-blind as well as drivers with perfect vision.  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.

The professor 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.  Drivers with perfect vision will hardly notice the pink X that is set within the red signal, particularly from a distance, but red-green colour-blind divers are able to easily distinguish the contrasting blue X against a background that they perceive as being yellow.  Research shows that the mark is clear even from a distance.

Colour-blindness affects around 8% of males and 0.5%  of females, with most people with the condition experiencing problems differentiating between red and green.

More at TTel