By Jared Ebersole in Video — 09 Feb 2026

Red Lights Were Invented to Make Cities Faster

The modern traffic light is not just a stop signal. It is a timing system that turned city traffic into choreography.

A red light feels like a city telling you no.

But the whole point of the traffic signal was the opposite. It was built to make the city say yes in sequence: this block, then the next block, then the next, with just enough order to keep every intersection from collapsing into the one before it.

Where it is

A key early New York traffic-signal location was Fifth Avenue and 42nd Street, New York, NY 10036. The video was planned around the Fifth Avenue corridor, including 34th Street and Fifth Avenue.

Before the light, the intersection was a negotiation. Horses, pedestrians, streetcars, delivery wagons, early automobiles, and police officers all shared the same space. A traffic cop could make sense of one corner with hand signals, whistles, and presence. That worked while the problem was local. It failed when the problem became a grid.

Cars did not just add speed to the street. They added volume, hesitation, and chain reactions. If one intersection jammed, the next intersection inherited the problem. Then the next one did too. A human officer could stop and release traffic, but he could not easily coordinate a whole avenue as a single machine.

That is why the traffic light mattered. Cleveland installed an early electric red-and-green signal in 1914 at Euclid Avenue and East 105th Street. It was still close to the police model: the machine helped a human controller. The great leap was not merely replacing a person with a lamp. It was realizing that intersections could be linked, timed, and made to behave as a system.

New York's Fifth Avenue became a famous laboratory for that idea. In the early 1920s, the city experimented with traffic towers and coordinated signals along the avenue. The promise was simple and almost magical: drive at the intended speed and the city would open in front of you. Hit the first green, then the next, then the next. Engineers would later call this a green wave, but the appeal was obvious before the phrase was.

The reported improvement was enormous. Contemporary accounts and later histories describe Fifth Avenue travel between 57th and 34th streets falling from roughly 40 minutes to about 15 after the signal system and one-way traffic controls were introduced. That number is not just about lamps. It is about timing, street direction, enforcement, and the decision to treat traffic as a network.

The yellow light solved a different problem: uncertainty.

Early two-color signals could be brutal. A driver approaching on green had no built-in warning that the intersection was about to change. The choice was bad either way: brake hard and risk a rear-end crash, or push through and risk cross traffic. Yellow created a small buffer between permission and prohibition. It turned the signal from a command into a sentence with punctuation.

The modern three-color traffic light emerged through several overlapping experiments. Detroit police officer William Potts is widely credited with a three-color, four-way signal in 1920. Garrett Morgan patented an influential three-position traffic signal in 1923 that created an all-direction pause between movements. New York's towers and coordinated avenue timing made the signal visible as an urban system, not just a gadget on a pole.

That mix is why the traffic light is easy to misunderstand. We tend to see the red lens because we are the ones waiting under it. The city sees the cycle. Red on one street is green on another. A delay at one corner can be a release two blocks away. The signal is not designed to maximize any one driver's moment. It is designed to keep the whole street from becoming a negotiation every ten seconds.

The strange genius of the traffic light is that it made stopping part of movement.

It gave cities a rhythm that could be repeated, taught, enforced, and scaled. More than a century later, even smart signals and adaptive systems still begin with that same bargain: everyone gives up a little freedom at the corner so the larger city can keep moving.