How Red, Yellow and Green Became the Colors of Traffic ...
Do you ever wonder why our stoplights designate red as stop and green as go? Me too! In fact, it was my daughter's question on this very matter that inspired me to do some historic research.
Jim Cameron
In the early days of the railway, British railroads adopted a signaling system using flags, lamps, and semaphores where red indicated danger, white represented safety, and green conveyed a cautious proceed. This system borrowed elements from early industrial applications where red was used to signify a stopped machine while green indicated an active one.
However, a significant incident arose when a red glass lens fell from one of the signal lamps, inadvertently allowing white light to shine through. This mishap resulted in a collision due to confusion over the signal. Consequently, the decision was made to implement yellow as a new cautionary color.
Historically, red has been associated with danger, while green is considered calming. The choice of these colors also aligns with optical physics principles. Red light boasts the longest wavelength in the visible spectrum, rendering it less likely to be scattered by atmospheric elements like fog or dust. As a result, red light penetrates these conditions more effectively, making it an optimal choice for visibility in adverse weather.
By the 1860s, traffic congestion in London caused officials to seek solutions for regulating horse-drawn carriages, leading to the adoption of color-coded semaphore signals inspired by the rail system. Initially, policemen manned these signals from kiosks at intersections to direct traffic manually.
In the early 1920s, it was American police officer William Potts who pioneered the first traffic lights in Detroit, Michigan. Despite their revolutionary nature, these lights were still regulated by a human officer, which proved costly for traffic management. The evolution of traffic signal control soon took a leap with the introduction of timer-based systems. Some early signals even utilized sound; cars would trigger a timer to change the signal to green for a brief ten-second window when they honked their horns as they approached. This method, however, presented considerable logistical challenges.
By the mid-20th century, the Federal Highway Administration standardized traffic signals across the nation, mandating the use of the red, yellow, and green combinations we recognize today. In contemporary traffic management, advanced timer systems and sophisticated measurements such as inductive loops embedded in the pavement are now commonplace. These loops detect the presence of vehicles waiting for a green light, ensuring a more efficient flow of traffic.
Today's traffic lights have undergone significant enhancements as well. They are designed to be visible in various weather conditions and have switched from incandescent bulbs, which needed frequent replacements, to durable LED lamps that consume far less energy while providing ample illumination.
Furthermore, at many intersections in Connecticut, there are sensors that detect emergency vehicles, allowing them priority at traffic signals by bypassing normal cycles. To assist the approximately 13 million Americans with color blindness, standardization dictates that red lights are installed at the top and green at the bottom.
Given the intricate technology invested in modern traffic signal systems, they do not come cheaply; the cost for a fully equipped signal installation can run as high as $8,000.
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Jim Cameron has been a Darien resident for more than 25 years. He is the founder of the Commuter Action Group, sits on the Merritt Parkway Conservancy board and also serves on the Darien RTM and as program director for Darien TV79. The opinions expressed in this column, republished with permission of Hearst CT Media, are solely his own. You can reach him at.