A 101 Year History of the Electric Traffic Signal System

November 10, 2015

As this year marks the 101st anniversary of the electric traffic signal, KAI’s Shaun Quayle, PE, describes the very first system and just how much signal systems have evolved since then.

The first traffic signal in the United States was shaped like a birdhouse with a switch on the post that was operated manually by a police officer. The officer used a toggle switch to change the light from green to red. There was no yellow indication at the time.

“If you had that situation today, it would be utter chaos,” says Shaun, a senior engineer in KAI’s Portland office who specializes in traffic signal system design and operations and intelligent transportation systems.

The first traffic light was unveiled in London outside the Houses of Parliament. The early lights were powered by gas, which proved to be disastrous when a leak in a gas line caused a signal to explode and seriously injured the police officer operating the lights, according to the Telegraph newspaper.

The original systems were not only more dangerous for the police officers and motorists alike, but a contrast between modern traffic signal systems and a human directing traffic shows that human direction makes traffic move more slowly, Shaun notes.

Americans fine-tuned traffic signal design during the early part of the 1900s, adding electric power, bells to let drivers know when the indications were going to change, and, ultimately, the yellow light.

Shaun says that in addition to improving the flow, efficiency and safety of traffic, computerized signal systems also allowed people to move to suburban areas because improved traffic control led to faster commute times for those who drove into downtown areas to work.

Today we have smarter “adaptive” signal control to better manage traffic and prioritize movements or vehicles on the roadway, such as fire trucks, ambulances or even buses. These smarter modern traffic signal systems offer huge benefits at a much lower cost when compared to widening roadways to achieve the goal of easing traffic congestion and improving safety.

Shaun notes that signal systems will continue to improve with advances in connected-vehicle technology.

“What we’re seeing is automakers connected-vehicle technology,” he says. Connected-vehicles provide more access to inform drivers of a variety of information including their expected wait time (countdown to green) to warnings of red-light running vehicles (see videos here). This information will also be available to traffic signals, providing more information to improve traffic signal operations. “That’s exciting for us because it allows us to optimize the system even more and move traffic through more safely and efficiently, improving the quality of life of all travelers,” Shaun says.

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