Electric traffic light

The electric traffic light emerged in 1912 Salt Lake City not because someone had a bright idea, but because automobiles had finally reached the density where human-directed traffic became impossible. The city's trolley system had already electrified the downtown intersections, providing the power infrastructure. The existing gas-lit traffic signals, first deployed in London in 1868, had proven the concept but required constant human attention and occasionally exploded. The incandescent light bulb, perfected three decades earlier, offered a safer alternative.

Lester Wire, a 24-year-old police officer newly appointed to the city's first traffic enforcement unit, built his prototype from a yellow wooden box with a pitched roof. He dipped incandescent bulbs in red and green paint—colors already standardized by maritime and railway signals, a classic case of path dependence where existing conventions shaped new technology. The device mounted atop a 10-foot pole, wired directly to the trolley system's electrical lines, and required a police officer in a nearby booth to manually switch the signals.

The public reception was decidedly mixed. Motorists unfamiliar with the concept simply ignored it. Pedestrians gathered to mock what they called "Wire's bird cage" or "Wire's pigeon house," pretending the box contained birds. Yet within five years, Salt Lake City had developed the first interconnected traffic signal system in the United States, with Wire's manual light automated by 1924.

The invention illustrates convergent evolution in technology. Garrett Morgan in Cleveland, unaware of Wire's work, independently developed a three-way traffic signal and became the first to patent the concept in 1923. His design added a third position—a pause between stop and go—that allowed pedestrians to cross safely. Morgan sold his patent to General Electric, which began mass production and established the standard that would spread globally.

Wire never patented his invention, and history largely forgot him. But his traffic light demonstrates the adjacent possible in action: the technology could only emerge when electric power infrastructure, standardized signaling conventions, and urban automobile density converged. The invention wasn't waiting for an inventor—it was waiting for the conditions that made it inevitable.

Today, traffic signals coordinate with sensors, cameras, and AI systems that Wire could never have imagined. Yet the basic concept—colored lights controlling vehicle flow—remains unchanged, a testament to how early design choices lock in for generations through path dependence.