Saturday, May 23, 2009

Grey Means Go: An Introduction


The issue of color vision deficiency been largely ignored by transportation professionals. An estimated 6-12% of the male population has some sort of colorblindness, meaning roughly 5% of road users are affected. The effects are not well documented, but what is known is that color deficient drivers suffer a disadvantage on the roadway.

The topic is important because 90% of what drivers use to navigate is visual, and much of that information is color-specific. Traffic sign types are denoted by color, and pavement markings in the United States have different meanings if they are striped white vs. yellow. Traffic signals’ red and green indications -- the two colors most often confused by color-deficient individuals -- provide drivers with opposite messages: Red means stop. Green means go.

But to a color-deficient driver, and even more so to a true color blind driver, the colors have little or no meaning.

Grey means stop. Grey means go.

The purpose of Grey Means Go is multi-faceted:

1. Describe the problem and share the small amount of research literature available on color deficiency in transportation and advocate for additional studies on the topic.

2. Share best practices that have been implemented – mostly outside the United States – to help colorblind drivers:

3. Encourage transportation professionals to consider color-deficient road users during design, construction, and operation of transportation facilities.

4. Encourage readers to share their stories of driving with color deficiencies, with the hope of increased community and discussion of this important issue.

So please take the time to read through the blog, make comments, and tell your stories. How does colorblindness affect you on the road?


I'm also always looking for guest bloggers, so feel free to contact me directly via e-mail at chandlerb22@gmail.com.

11 comments:

  1. I first became aware of the signal issue when I took a trip with a color blind colleague to a city with horizontal lights, instead of the vertical ones he was used to. It took some adjustment and help from me for him to figure them out. But it never occurred to me that at night it's much harder to distinguish by position, without the outline of the overall signal visible. Reflective borders sound better than nothing, but if your headlights are aimed right, they won't light up a retroreflector mounted high above the street. With LEDs, it would be technically easy to implement a thin illuminated strip around the border of the signal. That would seem to me a much better solution.

    ReplyDelete
  2. Charlie - Good point regarding reflective signal borders. Headlamps are pointing much lower these days than in the past, and with the signal heads so high in the air they could still be missed.

    I like the idea of LEDs for this purpose. Power is already running up there to supply the Red-Yellow-Green. It seems like a minimal addition to light up a border.

    Thanks for the post!

    ReplyDelete
  3. As a peson with full colour vision, I prefer that all drivers are at least able to distinguish red yellow and green, especally if they are carrying passengers. Why?
    First of all, red green colour-blindness is the most common and is male only. So if a red green colour-blind man has a wife (who probably hass full-colour vision and is almost certainly able to distinguish red yellow and green), and they are both in the car together, then for her to drive him around seems like a better default thna the other way round.

    ReplyDelete
  4. Myrtone - interesting observation. Part of the issue, though, is that up to 5% of male drivers have some sort of vision deficiency. In the U.S. alone, that would means millions of people would be unable to drive vehicles (including yours truly).

    The other piece, though, is that "color blind" is not so clearly defined. Various types of color deficiency exist, and each type has levels of deficiency. For example, I don't see a green traffic signal as green (it looks more white to me), but it doesn't look much like a red signal, so I'm able to tell the difference.

    Thanks for the comment.

    ReplyDelete
  5. Thanks for your response.
    "Part of the issue, though, is that up to 5% of male drivers have some sort of vision deficiency. In the U.S. alone, that would means millions of people would be unable to drive vehicles (including yours truly)."

    I assume you mean 5% of the all the drivers in the country, does the percentage, on a more local scale, vary from state to state? If so much information is more relevant to juristictinos with higher percetages of drivers with color defficiencies.

    "The other piece, though, is that "color blind" is not so clearly defined. Various types of color deficiency exist, and each type has levels of deficiency."

    I was aware of that, and I gave one type in my example.

    "For example, I don't see a green traffic signal as green (it looks more white to me), but it doesn't look much like a red signal, so I'm able to tell the difference."

    As long as yellow and red look different from each other and from green, then good for your driving. The earliest train signals were also white, green and red, this was changed because of drivers confusing white with starlight. So they substituted yellow for green and green for white. So I hope you are greatful that our traffic lights don't distinguish between green and white.

    And why would the portions vary form state to state? One is that the portions of color defficient people who self-drive might vary accoring to factors like the availability of alternative transport.
    Also, the portion of the population that are color defficient might also vary between different places. One reason is that the total prevelance of all colour defficiencies and the relative portions of differet types of colour defficency might vary according to race, as many other things do.

    ReplyDelete
  6. Regarding the variance among states, it's nearly impossible to know, as color deficiency is rarely officially diagnosed or treated. I've never had an optometrist deem me colorblind, but when I look at an Ishihara Test (the one with all the little circles), it's quite obvious.

    I'm sure there are variances among regions, races, and other factors, not to mention your comment about alternative transportation.

    I am quite grateful that Green and White aren't both used for traffic signals. I'm also grateful that traffic engineers over time have adopted other standards (e.g., Red is always on the top of the signal, most signs do not require color vision to be understood) so as not to exclude those with color vision deficiencies.

    Thanks for continuing the conversation. I enjoy it.

    ReplyDelete
  7. "Red is always on the top of the signal"
    I have read about the reason for this, the idea is for red the be visible as far back as possible. I also note that until recently, with the advent of LEDs it wasn't technically feasible to have different colour aspects in the same position, but now Ontario does this with it's turn arrows in places, and as long as those who don't read the difference don't drive it should all be fine.
    But you seem to be saying there are too many of you for this to be the case. Remember that passengers carried in a personal car might be too young to drive or may not be permitted to drive for some other reason such as a visual impairment different from and much worse than colour deficiency.
    When it comes to accommodating road users with visual or visual processing impairment, there's a road rule in New Zealand which might be of interest:
    Say you come to an intersection and there is a car coming the other way turing left (which would be a right to them, and note that New Zealanders drive on the left). Now if you are going straight, same as usual, they yield to you. But if you are intending on a left (curb) turn and you are both going the same way, you are to yield to them.

    See this video.

    ReplyDelete
  8. I've run across those LED signals as well, and gotten through them with some difficulty (or help from a passenger, if I'm not alone in the vehicle).

    In some U.S. states the left-turning vehicle has the right-of-way over an opposing right turn driver. If there are multiple lanes available for the turns, sometimes the turners each have the right-of-way to their lane (inside lane for the left-turner, curb lane for the right-turner).

    ReplyDelete
  9. "In some U.S. states the left-turning vehicle has the right-of-way over an opposing right turn driver."

    I thought New Zealand was the only country with this rule, could you be thinking of the Pittsburgh left. The reason for mentioning this specific rule is that applying the rule means that the left turning driver has to be able to recognise the other drivers intetions to turn right in order to know they are required to give way. This requires recognising directional indicators. Can colour defficency make these any harder to see, at lest if the headlights are on?

    ReplyDelete
  10. In one particular situation, the right turning vehicle is separated by a small delineator island and the Yield sign. This, obviously, causes that right turner to yield to the opposing left turn traffic.

    Without that island, it does get trickier. I'm not familiar with the term "Pittsburgh left," but I'm curious what it is.

    I can't speak for all color deficient drivers, but direction indicators on vehicles aren't difficult for me to see.

    I wrote a couple years ago on tail light color; it was in response to a research project I ran across at some point.

    http://greymeansgo.blogspot.com/2009/03/red-vs-yellow-tail-lamps.html

    ReplyDelete
  11. Also I found out another thing, but let me first mention that achromotopia is linked to very low visual acuity, typically around 20/100, so current US traffic law effecitvely excludes them from driving.
    What I learnt is that many of the problems that those with even mild forms of colour defficency have has to do with the colour-background combination rather than the colour itself.
    Thus deurotanomally can affect the distance at which one can tell if raspberries are ripe.
    This suggests that that the "Driver's test line" should be higher (than 20/40) if one is colour defficient, and perhaps depend on the magnitude of the colour defficiency.

    ReplyDelete