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Sorry Protanopes – hope you didn’t want to see that plate!

There was a time in North Carolina when the license plates were issued as white plates with blue lettering. Times have changed – a new era has arrived. If any of you live in North Carolina and have purchased a new car recently and/or needed to request a new plate in the last year, you may have noticed that the lettering is now red. As a member of the human factors profession, I cringed when I saw the first plate on the road. This must be a mistake – no way would the state be issuing plates in red font!!!

Why is this such a concern, you may ask? Well, my first concern was for the protanopes in North Carolina. Protanomaly is a dysfunction of the cones in the human visual system. It causes a weakness in viewing red in the color spectrum. Its more extreme form, protanopia, is a condition in which an individual is missing the cones needed to see red. Individuals with this condition have difficulty distinguishing red; however, they are typically able to distinguish other colors such as blue reasonably well. So, why did we change?

You may be thinking to yourself, well very few individuals have some form of color vision weakness (frequently, but incorrectly, called color “blindness”). This is true. Roughly 4% of the population are color weak with 8% of males having some form of color weakness. There is another population to consider, however, the remaining 96% of the population. While not color weak, people with normal vision still can have issues viewing red lettering, especially at night.

At night, all of us rely on “scotopic vision.” Our visual system acts a bit differently at night than during the day with our rods (our receptors that see in black and white) accommodating much more quickly in the dark than our cones (our receptors that see in color). This is why at night you primarily see in shades of gray.

In essence, it is difficult for the visual system to accommodate quickly to red lettering at night. Many displays in both airplane cockpits and automobiles are now using blue and/or green lights rather than red for this same reason. So, what are the practical implications of using red lettering on our license plates? Well, if you are the witness of a hit and run that occurs at night, for instance, it may take you longer to “see” the license plate number. By the time your visual system has accommodated, the car may have already left the scene. It is a hit and run! In a similar hypothetical event, an officer may need to record the license plate number of a vehicle. This simple task can be difficult during the day for a protanope and difficult at night for the rest of us.

Poor design decisions like that of using red license plate lettering could have been prevented if human factors professionals were involved. Pointing out the implications of these decisions will hopefully lead to the realization that there are many venues where the human factors profession can and should make an impact. It is important that our professional community make itself better known and understood. We are making strides in this regard, but examples such as the new license plate lettering indicate that we still have a long way to go.

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About Christina Mendat

Christina Mendat, Ph.D. is a Senior Human Factors Specialist and project lead at HumanCentric. She has 5 years experience in the human factors profession. She brings expertise in, product design, ergonomics and anthropometrics, software interface design, tactile interface design, workflow assessment and usability testing in all product areas.

Christina has been involved a wide-array of projects including, but not limited to: Voice Recognition Systems, E911 Call Center Software, Ultrasound Workflow Evaluations, Zero Turn Riding Mower Ergonomic Redesign, Cellular Phone Media Interfaces, Digital Frame UI Design and Global Focus Group Studies.

One of Christina's core competencies is in parametric statistics and leveraging those techniques in many subject areas. Some of Christina's main interests include: agricultural machinery, older adults and technology, haptic interfaces, and e-learning. Christina holds a Ph.D. and M.S. in Experimental/Ergonomics Psychology from North Carolina State University. She is a member of the national Human Factors and Ergonomics Society (HFES) and Tactile Research Group.