How Traffic Lights Work
We have come a long way since the horse and buggy days of our ancestors. Even today we barely even notice the infinite number of traffic signals, unless we are in a hurry and they all seem to turn red as we approach them. Who invented these signal devices and just what makes them work? Here are a few interesting facts that you can ponder the next time you are sitting at a stop light.
Long before the automobile was being driven the issue with traffic safety still existed, despite the fact that the traffic was wagons, buggy's and pedestrians. So much so, that the world's first traffic light came into existence and was installed at an intersection in London in the year 1868. The light was actually a revolving lantern with red and green signals that was illuminated by gas, and operated by man power by turning a lever at it's base just at the right time for the traffic to flow. Unfortunately, this device blew up and injured the police officer that was operating it at the time in January of 1869.
As the automobile started making it's presence, the amount of traffic became worse and along with that came the issue of everyone's safety while on the road. One local Detroit, Michigan police officer, by the name of William L. Potts, became overly concerned and decided to do something about it. He came up with an idea of adapting the current railroad signals for street use. Officer Potts used red, amber and green railroad lights, roughly $37.00 worth of wire and electrical parts and created the world's first 4-way three color traffic signal. Not long after in 1920, it was installed at a local intersection in Detroit. Within the following year, another fourteen of his automatic traffic lights were installed.
Around the same time, a very talented inventor, named Garrett Morgan, and supposedly the first African American to own an car, realized the same need for traffic control in Cleveland, Ohio. He invented an electric traffic light, that looked like the semaphore signals that we see today at railroad crossings. He wasn't the first man to obtain a US Patent for Traffic Signals, but he was the first one to sell his patent to General Electric Corporation for $40,000.
Traffic signaling devices have been installed in cities around the world for the purpose of controlling the flow of traffic. The most common lights consist of those with a set of three lights: red, amber and green. There are many different kinds of traffic signals and they are used differently according to the country they are in, and the special requirements of a particular area of traffic flow and congestion. There may be special lights for pedestrians, to let them know when it is safe to cross a street with some being equipped with a computerized voice to assist the blind. There may also be signals for bicyclists and buses. Their light sequences may vary and they may have extra lights on them for traffic that is turning in a particular direction. Larger and more complex intersections may use a combination of these.
Prior to the mid-1990s traffic signaling devices were equipped with either incandescent or halogen light bulbs. Since then the development of lamps using light-emitting diodes, or LEDs are used, and have many advantages over the incandescent light bulbs including, they are highly energy efficient as they can be solar-powered, they last much longer which means less replacement costs, they shine brighter, they switch faster, which is important if you are in a hurry and don't like to wait, and the operational costs are much lower than the incandescent lights.
In addition, many traffic signals today are outfitted with Traffic Signal Preemption systems that allow emergency vehicles the ability to change the traffic signals from red to green, and to change the signals for the opposite direction from green to red, therefore enabling them to respond more quickly and safely to their destination.
As well as the traffic signals themselves, there is also a complex timing system that they are connected to. By sensors being placed either in the road or on the traffic devices themselves, they can detect when there are vehicles present at the intersection which in turn informs them to change the color of the signal.
So the next time you are having to sit at a red light, think about those who created the traffic signal. And even if you are in a hurry, remember that these traffic signalling devices are for your safety and that they do save lives every year.
