If you drive in town, you know the frustration of being in a hurry and hitting a series of red lights. Although the contemporary traffic light controller is designed to mitigate that common frustration by responding directly to traffic flow, that was not always true. Until recently, traffic control systems typically created more traffic snarls than they prevented.
How Traffic Control Evolved
The problem of controlling traffic did not begin with the invention of the automobile. It dates to the days of horses and carriages.
When horses dominated the roads, police officers would direct traffic at the busiest intersections, making sure that horse-drawn conveyances and pedestrians alike could navigate city streets safely. It wasn’t until 1868 that London obtained its first non-human traffic light controller. It was located at an intersection near Parliament.
This pioneering machine featured red and green lenses with gas-powered lighting. It had arm extensions that pointed traffic in the right direction. The traffic director positioned the arms and lit the lights to help maintain an orderly traffic flow.
The first electric-powered traffic controller appeared early in the 20th century, but the traffic officer still had to manually select colours as necessary. In 1920, a policeman from Detroit, Mich. invented the first four-way traffic light, basing his design on the railroad signals already in use. Cities employed this popular device for decades. Each signal box contained its own controller that changed the lights from green to yellow to red at regular intervals.
Signals with Sensors
The problem with the electronic signal was that its orderly on and off pattern did not reflect traffic ebb and flow. As a result:
• A lone driver would have to stop at a red light even if no one else was on the road.
• Motorists at the end of a long line of vehicles might have to sit through several light changes.
• A traffic cop would still be necessary to direct drivers through intersections during exceptionally high-traffic events.
In the effort to address these problems, innovators came up with electro-mechanical controllers. Still in operation as of the end of the 20th century in some locations, this system relied on loop detectors embedded in the roadway that detected the presence of vehicles. The controller would change the light accordingly to let traffic through.
Although an improvement, this system was still problematic for those driving lightweight compact cars or motor scooters. Because the sensor loop could not always detect them, drivers might find themselves stuck at static red lights. Clearly, this system needed further refinement.
In time, innovators designed a traffic light controller programmed to predict daily periods of higher traffic flow. During those periods, it switched to a modified signal schedule. However, unpredictable events such as accidents could easily render such standardised scheduling moot.
Adaptive Traffic Control
Adaptive traffic control is based on network communication between traffic signals. This new technology adjusts the pattern of a single traffic light in response to unexpected events. Signals communicate with one another in a continuous stream of real-time traffic information, enabling them to adjust signal changes independently without the need for a central controller. Adaptive traffic control:
• Results in more efficient travel through the city
• Keeps driver frustrations and resulting errors at a minimum
• Prioritises the smooth passage of emergency vehicles
• Helps public transportation proceed more efficiently
• Enhances traffic flow while minimising congestion
Big cities with rapidly changing traffic issues and smaller municipalities that experience seasonal traffic surges both benefit from this smart technology. Fewer accidents, less driver frustration and the smoother delivery of vital emergency services help cities recoup the initial cost of a system upgrade in a relatively short period of time.