Ode to the Traffic Signal

Traffic signals have come a long way since the first gas-lit signal was installed in London. Today, nearly 150 years later, traffic signals are once again revolutionizing intersection safety and efficiency. Through heads-up displays and mobile apps, real-time signal information is improving the way we commute. This month, we honor the signal by looking back at its evolution.

The Early Days
The Invention of the Traffic Signal

Navigating the roads in the early 1900’s was a harrowing experience. Pedestrians, cyclists, horses and street cars shared the road without regulations making it immediately apparent that a system was needed to protect all users and keep traffic flowing.

In 1918, James Hodge patented what is largely considered the first traffic signal. The signal consisted of eight lights mounted on a corner post and a manually operated switch to ensure signals don't conflict with one another.

About the same time, Garrett Morgan also saw the need to control the flow of traffic after witnessing a horrible accident. His patented t-shaped electric, automatic traffic light was sold to General Electric for $40,000 in 1923.

Actuation
Responding to Demand

As is the American way, shortly after the advent of traffic lights, inventors began to explore ways to enhance their functionality. The first great challenge was determining how to activate signals in response to demand. The first to address this was a sound-based system invented by Charles Adler in 1928. Once at the intersection, a vehicle could honk into a pole-mounted microphone to inform the signal of its presence. 

Shortly after Adler’s invention, Henry A. Haugh developed the first pressure detector to send electrical impulses to the controller when two metal strips touched under the weight of a vehicle. In 1934, loop detectors were widely adopted and are still in use at many intersections today.

Want to learn more about signal actuation? Check out our Advanced Signal Timing Webinar for an in depth look at how technology is responding to traffic demands.

Synchronization
Central Control and Coordination

As time and technology progressed, the integration of computers made actuation even more effective by enabling the centralized monitoring and control of citywide signals. Though the first computer took control of 120 traffic lights as early as 1952, the first advanced traffic control system was not deployed until 1972 in Washington, DC, leveraging microprocessors, fiber optic cable, and inductive loops to connect and control timing at 113 intersections.

The ability to connect signals to each other has since led to the advent of signal synchronization solutions, such as adaptive technologies, that coordinate signals to move platoons of cars through a corridor more effectively .

Connected Vehicles
Looking Toward the Future

Today, connected and automated vehicles are once again redefining the role of traffic signals by taking the signal out of the intersection, and putting red and green time information into cars and mobile apps. 

Seeing how the traffic light has evolved and picturing where it will take us in the future is an exciting thing. At McCain, we are eager to be a part of connected vehicle technology and how it will shape the way we drive by taking part in a number of pilot studies, including Connected Vehicle to Everything of Tomorrow. 

To learn more about traffic control in a connected vehicle environment, grab a cup of coffee and watch our connected vehicle technology webinar.