Who Smarted? Podcast Summary
Episode: "Why are Traffic Lights Red, Yellow & Green?"
Release Date: May 14, 2025

Introduction

In this episode of "Who Smarted?", Trusty, an inquisitive young listener, finds himself waiting impatiently at a bustling intersection. Frustrated by the seemingly endless red light, Trusty strikes up a conversation with Trevor, the personified traffic light. This engaging dialogue sets the stage for an entertaining exploration into the history and science behind traffic lights.

The Origins of Traffic Lights

Trusty ([00:00]): "I'm just standing at the corner waiting to cross this busy street. ... But the light should turn green any second now."

Trevor ([00:30]): "No, not forever forever. It's actually on a timer, like all traffic lights."

Trusty’s curiosity leads him to question Trevor about the invention and functionality of traffic lights, particularly why they use the colors red, yellow, and green.

The First Traffic Light in London (1868)

Trevor ([03:28]): "The first traffic light was a far cry from what you see on the roads today. But it was a start."

Trevor explains that the very first traffic light was installed in London in 1868, right in front of the British Parliament buildings. At that time, horse-drawn carriages dominated the streets, leading to chaotic traffic and pedestrian congestion on Westminster Bridge. To manage the heavy traffic, the semaphore-based traffic light was introduced.

Semaphore System and Early Operations

Trusty ([05:17]): "Smarty pants. True or false? The first traffic light was powered by gas lamps and had to be manually controlled by a police officer. If you said true, you're right."

Trevor ([05:36]): "Semaphore is a signaling system in which a mechanical arm or flag extends from a pole. ... drivers needed to stop or go based on the arm's position."

The semaphore system involved mechanical arms and gas-powered lights, operated manually by a traffic cop. A horizontal arm signaled drivers to stop, while a 45-degree angle indicated it was safe to go. However, this system had its limitations, especially in low visibility conditions.

Transition to Electric Traffic Lights (1912)

Trevor ([09:24]): "The first electric traffic light was invented in the USA by a police officer named Lester Wei."

In 1912, the United States saw the advent of the first electric traffic light, significantly improving upon the semaphore system. This innovation marked a pivotal shift, making traffic management more efficient and reducing the reliance on manual control by police officers.

Introduction of the Yellow Light (1920)

Trusty ([13:22]): "So the first traffic light didn't have a yellow light? How did they warn drivers?"

Trevor ([14:13]): "Yes, the first traffic lights went straight from green to red. To address safety concerns, Officer William Potts introduced the yellow (amber) light in 1920."

Officer William Potts played a crucial role in enhancing traffic light functionality by adding the yellow light. This intermediate signal provided drivers with a warning to slow down before the light turned red, thereby improving safety at intersections.

Automation and the First Automatic Traffic Light (1922)

Trevor ([14:46]): "In 1922, the first automatic traffic light was installed in Houston, Texas. This system used built-in timers to control light changes."

The introduction of automatic traffic lights revolutionized traffic management by eliminating the need for manual operation. Houston's implementation of timer-based traffic lights allowed for more consistent and reliable regulation of traffic flow. This advancement also enabled the reallocation of police officers to other essential duties, saving significant municipal costs.

Modern Traffic Light Technology

Trevor ([15:30]): "Today's traffic lights do way more than just change colors. Sensors and automation help manage traffic flow effectively."

Modern traffic lights incorporate advanced technologies such as green waves and sensors:

• Green Waves ([15:40]): "A system where multiple traffic lights are coordinated to turn green in succession, allowing cars to pass through several intersections without stopping."

• Sensors and Induction Loops ([16:09]): "Digital sensors detect vehicles approaching an intersection, while induction loops embedded in the road sense the presence of vehicles to adjust light changes accordingly."

These innovations enhance traffic efficiency, reduce congestion, and improve overall safety on the roads.

Global Differences in Traffic Lights

Trusty ([16:47]): "Are all traffic lights the same worldwide, or are there differences?"

Trevor ([17:04]): "While many aspects are standardized for safety, some variations exist globally. For example, in Japan and Quebec, traffic lights are horizontal instead of vertical."

Key differences include:

• Orientation: Some countries use horizontal traffic lights, especially in regions where driving is on the left side of the road, like Japan.

• Color Ordering: In countries driving on the right (e.g., Canada), horizontal lights display red, amber, and green from left to right. Conversely, in left-driving countries, the order is reversed.

• Terminology: In South Africa, traffic lights are colloquially referred to as "robots."

Conclusion

By the end of the episode, Trusty gains a comprehensive understanding of the evolution of traffic lights, from their early semaphore origins to the sophisticated, automated systems in place today. The conversation underscores the importance of these devices in managing traffic flow, enhancing safety, and adapting to technological advancements worldwide.

Notable Quotes:

• Trevor ([03:28]): "The first traffic light was a far cry from what you see on the roads today. But it was a start."

• Trusty ([07:00]): "Smarty pants, any idea why those colors were used to represent stop and go?"

• Trevor ([15:30]): "Today's traffic lights do way more than just change colors. Sensors and automation help manage traffic flow effectively."

This episode of "Who Smarted?" successfully combines humor with insightful historical and scientific information, making the topic of traffic lights both educational and entertaining for young listeners and their families.

Credits:
Written by Phil Greenlight Jeremy
Voiced by Mike, Adam, Tex Davis, and others
Produced by Adam Tex Davis and Jerry Colbert
Technical Direction and Sound Design by Josh
Theme Song by Brian Mixed Signals Suarez with lyrics by Adam Tex Davis

Produced by Atomic Entertainment.