Shaped signal heads to aid colorblind drivers

This signal in Hallifax, Nova Scotia, incorporated various shapes to its traffic signals. This enhancement provides additional information to all drivers, and particularly helps colorblind road users traveling through the intersection.

It seems that a number of other countries have designed roadway elements and traffic control with colorblind users in mind. Unfortunately, consideration for colorblind drivers is rare in the United States.

A Signal Solution from Quebec

In Quebec, the authorities have developed a way to help colorblind drivers determine when the signal is red. The signal has two red indications, one on each side. All other indications (green and yellow balls, and any arrows) have a single indication.

Also note the reflectorized outline around the signal backplate. That low-cost countermeasure for colorblind drivers provides a significant benefit to all by increasing the conspicuity of the signal.

Colorblind Glasses

Apparently the problem was solved decades ago with the introduction of colorblind glasses. It's simple, really. As the article points out, the glasses block all green light from entering the eyes. Therefore, a colorblind driver knows that if he sees any light, it must be either red or yellow.

Yikes. Now, instead of a driver having some color confusion as he enters an intersection, he has true color blindess. Hopefully the vehicle in front of him isn't green.

This doesn't even get into issues like bulbs being burned out or other signal failures.

Luckily these didn't take off, and we're left to search for additional creative ways to help colorblind drivers navigate our roads.

Color Blindness & Green Traffic Signals

A 2003 Minnesota DOT study took a look at the color blindness affect with regard to traffic signals. The researchers specifically studied a green LED signal indication.

For quick background, states began installing Light-emiting diode (LED) traffic signals in the late 1990s. The LED bulb provides significant energy savings and longer life.

The problem was that the clear cover over the green indication "lit up" under direct sunlight. Because it appeared bright, it appeared to be ON to colorblind drivers, and it was so much brighter than the red or yellow indications that drivers would assume the signal was telling them to GO.

A person with color vision deficiency tends to use brightness - not color - as his most important cue at traffic signals (and a number of other situations). I personally tend to see green indications as bright white. This is usually not a problem, but can become one in the scenario discussed in this paper (I can also have trouble if there is a lot of background lighting - either street lights or advertisements - in line with the signal heads).

Minnesota DOT conducted a quick study (four colorblind participants and four non-colorblind) to test the theory that the current installation could be confusing to colorblind drivers. They found that 25% of the time the colorblind participant erroneously saw the green light ON when it was not (non-colorblind participants made this mistake less than 4% of the time).

The Minnesota short-term solution was to replace their clear covers with colored ones, which will hopefully make the green indication much less bright in direct sunlight. But the inherent problem remains that colorblind drivers (estimated at up to 5% of the population) are generally being ignored in traffic signal design, where color is the most important factor in keeping motorists safe.

See the full article here: http://tinyurl.com/greenLED

Why are we here?

The initial purpose of this blog is to share information and faciliate discussion about the needs of colorblind drivers, bicyclists, and pedestrians.

The percentage of colorbind people in the world is an oft-debated subject, as very few people are officially tested for color blindness. It's typically discovered by the individual themselves as they have trouble with certain color-related areas of life.

I'm a Traffic Safety Engineer and I'm red/green colorblind. Though I've worked in the transportation industry for over a decade, it has been rare to see an article, research project, or conference presentation on this issue. It is my hope to elevate the discussion and eventually improve roadway design and operation to improve the experience of colorblind roadway users.