All You Need to Know About Traffic Signal Controllers

How do traffic controllers work? There’s more than one type of traffic signal controller, and they each work a bit differently. The main types you’ll find include electro-mechanical controllers, hybrid controllers and electronic controllers. Here’s a basic guide with everything you need to know.

Electro-mechanical controllers

The electro-mechanical controllers were the earliest types of traffic signal controllers, but they’ve still been installed in traffic signaling systems up through the 2000s. They feature a rotating dial that’s similar to a standard kitchen timer, and more advanced models feature several dials that allow for different timings for different days. The dials are equipped with keys that activate a switch. During installation, gears are installed to control the speed of rotation of each dial.

As each key passes a microswitch, a motor is activated. As the motor communicates with other components in the signal system, it turns on the signal indicator on the street, indicating whether it’s safe for drivers or pedestrians to stop or proceed.

Hybrid controllers

These controllers can work well for fixed-time applications. They don’t handle actuation, responding to serve a vehicle or pedestrian. Timing is fixed and generated by vacuum tube electronics charging an oil-filled capacitor. The tube eventually discharges through the solenoid, moving the cams and changing the signal indicator. Knobs on the front of the controller are manually changed by hand, which controls the timing of the signals. In other words, these signals are less efficient because they don’t respond to serve a vehicle or pedestrian—timing is always fixed.

Electronic controllers

Electronic controllers can be connected to communications equipment like a master controller or a traffic control center. On the controller, there are status screens to show what the controller is doing, as well as programming screens where administrators can specify what the signal needs to do.

There are several features that can be programmed, including density and time of day programming. This allows administrators to create a signaling plan that responds to how many cars will be traveling through an intersection at a specific time of day. There are also sensors that can detect the number of cars waiting for a signal, and they communicate to change the traffic light.

While electronic controllers aren’t so advanced that they can detect several vehicles in camera range of the intersection, some can detect vehicle speed to turn the light red if a motorist is speeding. Traffic signaling systems still have a long way to go to be fully responsive to the needs of both motorists and pedestrians alike.

Traffic signal controllers are essential components for any traffic signaling system. Learning how traffic controllers work can be a complicated process. Whether you need to install a new signaling system or you’re upgrading a current one, reach out to Signal Equipment Company South. With several decades of experience serving the traffic signaling needs of municipalities, we can help you find the right equipment for your unique applications. We look forward to hearing from you soon and discussing your needs.