Thursday, February 9, 2012

Let There Be Light: Colorblind-Friendly Traffic Signal

According to a recent news report from the Mainichi Daily News, a university professor in Japan has developed prototype traffic signal LEDs that enable persons with red-green colorblindness to distinguish between red and yellow indications. Field tests are underway at several locations, including Fukuoka and Tokyo.

As seen in the photo, the red indication will include an "X" that doesn't show up predominantly to users with regular vision when they get close to the signal, but is easily distinguishable by red-green colorblind drivers.

We've discussed traffic signals quite a bit on Grey Means Go, including this recent post about a prototype for different-shaped traffic signals, and some actual installations of innovative treatments in Kentucky.

What do you think of the "X" red light in Japan? Helpful without distracting other drivers? Any concerns?


  1. Should they conduct a survey checking the colour vision of local road users before giving it the final green light?

    Will there be a blog post on the NZ right hand turn rule before the rule is finally changed, which will be 5 am on March 25?
    Say a protanope is driving in New Zealand and fails to give way when turing left because he fails to recognise the other driver's inteniton to turn right, because of the dimming effect.

  2. Here's an idea, how about making the signal heads square instead of round, as to exapand thi lit area, improve visibility, and make the X slightly larger.
    How about making the green phase a deeper green with a slightly bluish circle?

  3. Will the white X be visible from far enough away? Stopping sight distance is 495 feet on a 55 mph road.

  4. Myrtone - I agree that a square red light would be even better (see recent post on the circle/square/triangle signal), but it would take a significant effort over many years. Swapping out only the signal LED bulb could be a potentially very low cost change.

    Anon - I assume the X is designed to be as visible (in terms of SSD requirements) as the rest of the traffic signal indications.

  5. I know about that post, but in that design, each signal section is a different shape. In the design I was thinking of, all three would be square, as to make the lit area larger, while maintaining the spacing between them.
    The idea would be to incorporate a pink X into the red phase of Art Lebedev's design.

  6. The X is a good idea, but what about arrows? The US has red, yellow, and green arrows. Make the shaft of the red arrow magenta?

    The single section flashing red beacon is not a problem in the US. A STOP sign is required to be posted at each of these.

  7. One idea wolud be to have a black arrow on a red illuminated background.