We see them almost every day, but have you ever stopped to consider how big traffic lights actually are? Many are almost as tall as a person.
They can range in size, depending on the area where they are placed. A typical three-light pattern with an eight-inch lens is about 30 inches high when stacked on top of one another.
There are also stoplights with twelve-inch lenses that are more slender. These tend to be more popular in areas that have heavier traffic or where drivers need to be able to see them from a distance.
In the UK, most traffic lights operate on timers. They cycle through green, yellow and red at set intervals to provide sufficient green time for all lanes at an intersection.
The length of each color of light is dependent on the volume of traffic at an intersection, and is determined by a computer system inside the control box. In addition, traffic lights have sensors that detect vehicles approaching the intersection from each direction of travel.
These sensors are connected to an electrical circuit that is monitored by a computer inside the control box. When a car arrives, the sensor sends an electronic signal to the controller that tells it to change to the next color.
Some traffic lights use video cameras to help police identify offenders who break traffic laws. These systems are more expensive to install and maintain, but they can be a great way to improve safety and reduce traffic accidents.