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In the Beginning
There Were Signals
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The Evolution of
Signal Timing
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Dawn of Adaptive Signal Control
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Before the first car hit the road and well before the invention of the Model T, the traffic signal was already in use.
The first traffic light to manage intersections was designed in 1868 by J.P. Knight, and installed in London to regulate horse and wagon traffic, protecting pedestrians. The signal consisted of a tall post with moveable arms indicating "stop" when extended.
Almost 50 years later, the first automobile traffic light was invented. An improvement from its predecessor, the traffic signal was a manually operated, wooden box on a pole with red and green lights illuminated by electricity from nearby trolley lines.
Two years later, in 1914, an electric traffic light was developed resembling the modern traffic signal. However, it wasn't until 1920 that the four-way, three-color traffic signal was implemented.
Did you know? McCain has produced more than 5.6 million traffic signals. |
As a driver, it's easy to overlook the fine art of signal timing. We expect traffic lights to turn green as we approach the intersection, and when they don't, tempers rise by the second as we wait. But do we really have it that bad?
It wasn't very long ago that drivers would have to wait for traffic police to manually change signals based on personal judgment alone.
As the modern signal was introduced, an automated system was required to control timing. As a result, the fixed-time controller was invented, paving the road for the first traffic signal networks.
In 1924, the first attempt at networking took place in downtown Los Angeles. Thirty-one signals were operated from a central control station, becoming the first known traffic control center in the world.
As benefits of activating signals based on vehicle demand were acknowledged, the actuated intersection was developed.
In 1928, the first device to assign right-of-way using vehicle sensors was installed.
Shortly thereafter, a pressure sensitive detector was installed evolving into inductive loops, still used today.
Although, we still have problematic intersections, signal timing has come a long way. |
At the turn of the computer age, analog computer systems were used to apply actuated intersection control to signalized networks.
In 1960, a computer-controlled signal network was developed with the goal of equal distribution of green times. Soon after there was a big shift to digital computers due to reliability issues with analog systems.
The digital computer and microprocessor continued to drive the advancement of intersection technology, including the development of adaptive signal control.
In 1984, just shy of the Los Angeles Olympic Games, the first system to extensively monitor and manage traffic flow within a coordinated network was implemented.
The modern-day adaptive signal control solution is more dynamic and comprehensive than its 29-year-old predecessor. By optimizing signal timing on-the-fly based on current demand and system capacity, vehicles are moved faster and more efficiently than ever before.
Did you know?
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