03/27/2026
Fun Fact Friday
Color Blindness
Did you know that there is a historical connection between the early awareness and research of color vision deficiency (CVD) and railroad safety and procedures? As far back as the 17th century philosophers hypothesized the idea that people may not all perceive color in the same way. Only in 1794 did this idea begin to have scientific study with the first kind of objective testing being developed in 1837.
During the fateful midnight hours of November 15, 1875, near Lagerlunda, Sweden two oncoming passenger trains collided. Tragically 9 people lost their lives including the crews of both locomotives. Initially the investigation ruled that there was improper signaling by the station master who was sentenced to 6 months in prison. A year later in 1876 ophthalmologist (doctor specialized in comprehensive eye care) Dr. Frithiof Holmgren published a letter to the State Railroad Board which speculated that there may have been members of the crew with color vision deficiency and were unable to properly distinguish the difference between the red and green signal lantern indications. Although not officially recognized as the cause, this incident along with many other similar situations across the world motivated the pursuit of in-depth studies and research of the visual condition.
Dr. Holmgren, later simplified by Dr. William Thomson, developed color blindness screening tests which utilized pieces of yarn that were numbered and colored. This test was the first of its kind being used on railway employees to determine their ability to properly see the colored signaling with the goal of drastically reducing railway accidents.
With the success of these early screenings, along with the continued advancements of the research and understanding of the deficiency, it has become common worldwide to screen for color vision deficiencies. Recognizing the significance of the deficiency, many industries and regulatory agencies now require screenings of employees for initial and continued employment in positions that rely on proper color distinction. Some of the most notable jobs that restrict employment include railway, aviation and shipping because of the colored safety equipment and illuminated instrument panels as well as maintenance and electrical positions in automotive, aviation, and telecommunication industries for their extensive use of colored wiring.
Photos attached are of the Lagerlunda accident site which was taken a few days after the crash as well as an example of the colored railway signal lanterns from that period in time. Credit for the photos as well as much of the information in this post is courtesy of University of Cambridge’s publication “The Lagerlunda Collision and the Introduction
of Color Vision Testing”
