The size of each traffic light can vary depending on where it needs to be placed. They might seem small when suspended in midair, but even a traffic light lens is usually about the size of a human head!
Traffic lights usually range from 30 to 42 inches tall.
Lights with more lenses can be even taller than that.
Traffic light sizes and heights are dictated by state laws.
How big are traffic lights?
The average traffic light is between 30 and 42 inches tall—around four feet tall—but some are taller thanks to additional lenses. The lenses range in circumference from eight inches to 13.5 inches.
The most popular traffic light is the standard three-light pattern with eight-inch lenses. These traffic lights are about 9.5 inches wide and 30 inches tall.
What dictates the size of a traffic light?
Every state in the U.S. has its own laws regarding the size of a traffic light and its lenses. These laws also extend to where a traffic light can be placed and how high it should be above the road—usually 18 feet above the ground.
In addition, some states tailor traffic light regulations with budget costs being the primary concern. In either case, your state's Department of Transportation ensures that these regulations are followed.
In areas with heavier traffic, municipalities will err on the side of caution and opt for twelve-inch lenses. This improves the likelihood that the lights will be seen from any distance.
Cities with lower speed limits and driver populations often do just fine with eight-inch lenses.
. However, this doesn't mean that only the biggest traffic lights are useful.
Actually, many states prefer to use eight-inch lenses because they have more customizable features compared to twelve-inch lenses.
That's also the main reason why you usually only see eight-inch traffic light lenses in the United Kingdom. They can be manufactured with high visibility lenses, allowing drivers to see them from very far away, even when driving in bad weather.
While not as popular, hybrid stoplights with both eight- and twelve-inch lenses can be seen in Canada.