Friday, May 29, 2009

Can colorblind drivers see bicyclists?

Drivers often find it difficult to see bicyclists on the road, so extensive efforts have been made to increase bike-riders' conspicuity with hats, vests, jackets, and other high-visibility clothing. The researcher took a look at the color used for this apparel (often fluorescent green, pink, or yellow) to determine if it was visible to those with color deficient vision.

The results were neither statistically significant or overwhelming, but the author raises some interesting questions about the assumptions made by those producing, selling, and using high visibility garments. A photo example, using the Vischeck website to simulate color blindness, is telling:

The screenshot is from a website promoting high-visibility garments for kids. The "regular vision" screenshot is on the left. The "color-blind" simulation is on the right (I think).
I'm hoping this turned out well, because being colorblind, they look pretty much the same to me. I guess that's the point. According the author (whose word I'll take on this one),
"...most of it just doesn't work for people who are color blind. The
high-visibility green and orange hats become a light color that blends well with
the trees. The hot pink becomes grey."

I once led my state's work zone safety efforts for the Department of Transportation. It never dawned on me that I was seeing high-visibility vests very differently than those who were relying on them to stay safe in highway construction zones. With upwards of 5%+ drivers suffering from some color vision deficiency, it seems that colors most visible to the colorblind driver would be the most appropriate to use.

For the full report from Mr. Sullivan, click here.

Saturday, May 23, 2009

A great colorblind website

Daniel Flück of Zürich, Switzerland, started Colblindor in 2006. It is a great overall website on colorblindness and how we as colorblind people deal with this deficiency.

The site includes colorblind tests, news, and tools to support life with color deficiency.

I highly recommend checking the site out when you get a chance:

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

Friday, May 8, 2009

Helping colorblind drivers helps everybody

I previously referenced this study from the Kentucky Transportation Center regarding a number of low-cost safety measures for signalized intersections. Here's the complete document:

I took a closer look at it this week and noticed something interesting. A number of colorblind-friendly treatments also provided an overall benefit to the safety at signals.

Double Red Lights

This application creates a "Red T" at the top of the signal head. It's main purpose is to double the visibility of the red indication. For colorblind drivers, it provides additional information that it is the red indication (in addition to its placement at the top of the signal).
  • Total crashes down 2 per year
  • Angle crashes down 1.7 per year
  • Rear-end crashes up 0.5 per year

Advanced Warning Flashers

I had not thought about this one before as a significant colorblind benefit, but I believe it could be. There are times that I don't always know if what I'm seeing three blocks ahead is a traffic signal or just ambient lighting from other sources. Signal Ahead signs (and particularly those discussed in the report with actuated flashers) give me the additional information I need to know what is coming up.

  • Total crashes down 1.4 per year
  • Angle crashes down 0.7 per year
  • Rear-end crashes down 0.6 per year

Reflective Backplates

Backplate installation showed a crash reduction benefit for ALL drivers by adding conspicuity to the traffic signal.

  • Total crashes down 1 per year
  • Angle crashes down 0.4 per year
  • Rear-end crashes down 0.3 per year
Crash Data

Though the reductions seem small, it's important to keep in mind the cost was also very low for these treatments. And though 0.5 crashes per year might sound insignificant, if multiplied times an entire state DOT or large city signal system (sometimes thousands of intersections), significant reductions could be achieved.

The best implementation plan may be modifying policy so any new signal installations (or updgrades) are put in with these measures. High crash locations could also be added to the mix, so that eventually every signal includes these improvements or something similar.