How Do Traffic Light Control Systems Actually Work?

Most drivers don’t think much about traffic light control systems and how they work—unless they’re stuck at a seemingly endless red light. Believe it or not, this technology has been around for about a century, and as a result is by no means perfect. Traffic lights require careful timing based on historical traffic data and current research. When one is “off,” it can cause delays and traffic jams.

Here’s how traffic light control systems work.

Principles of traffic lights

Traffic lights are designed to safely manage vehicle, bicycle and pedestrian traffic. There are two main types: fixed time and dynamic control.

Fixed time traffic signals use a timer to change the lights at a fixed interval. They could be as short as 30 seconds or as long as several minutes, depending on the intersection’s historical traffic data. These traffic lights use an electro-mechanical signal controller, which has movable components and a dial timer. This allows the light to switch and hold light colors for the predetermined amount of time.

Dynamic traffic light control systems work by adapting their timing to current traffic conditions. They use a detector, which can communicate with the traffic light control system to let them know about current traffic. When an intersection is jammed, they’ll adjust timing to let traffic flow better.

Dynamic systems use detectors both in the road’s surface and above the light. When a car drives over the road-embedded detector, it sends a signal to the control system. This tells the system whether just one car is waiting to go through the intersection, multiple cars or none at all. You’ve probably noticed this effect before. If you’ve ever driven up to an empty intersection and the light magically turned green, that doesn’t necessarily mean you’ve perfected your telekinetic powers. It’s usually because the detectors above and beneath the road have “seen” your car and adjusted the timing accordingly.

These systems use a relatively complex system that allows all the lights in an intersection to communicate with one another. Otherwise, they’d run the risk of causing accidents. Generally, they include a main controller, control circuit, timer, clock signal generator, decoder, decoder drive circuit and digital display decoder drive circuit. Each component plays a critical role in detecting current traffic and communicating the message to the main controller, which relays the message to other traffic lights.

Of course, dynamic systems are more expensive to install and maintain, due to the sensors. Not every municipality is equipped to install them (or their even more sophisticated counterparts, smart traffic lights). They may be configured differently based on each intersection’s needs and who manufactured the equipment.

In the end, the type of traffic light control system you use depends on budget, traffic levels and other municipal concerns.

Now that you know more about the principles of how traffic light control systems work, why not get in touch with the experts to learn more? Signal Equipment Company South is happy to discuss the intricacies of our signal light manufacturing. Call today to get started.