How Traffic Light Control Systems Work
We've all heard of traffic lights and chances are that most drivers hate them from the bottom of their souls. They block you from reaching the destination faster, they make you burn more gas and sometimes, they force you to wait for several minutes in a huge traffic jam at a larger intersection.
But beyond these terrible scenarios, we must accept that traffic lights are playing a key role, not only for the overall safety of traffic, but also for pedestrians who wish to cross a road without putting their lives at risk.
While there are multiple traffic lights systems around the world, we're not going to talk about them, but about the way they are controlled or, if you prefer, the magic that lies underneath their cases or the spell that makes them turn green when a car approaches.
Although in some regions authorities and various companies have started testing innovative traffic light control systems, there are usually two different modes adopted by most nations on the planet: fixed time and dynamic control. Let's take them one a time and see the differences.
We won't get too technical and display every single part of such a system, but it's worth mentioning that fixed time traffic light control systems relied on what it's being called an electro-mechanical signal controller. In plain English, it's a less complicated controller with components that can move (hence the “mechanical” term), but also with dial timers to be able to keep a specific color for a given period of time.
Dynamic traffic light control systems on the other hand are more appropriate for the crowded traffic we're facing every morning, as they have been developed specifically to be able to adapt their settings to traffic conditions. In case you're driving at a rush hour and you're seeing green all the way from office to home, you're in luck: dynamic signals have turned all traffic lights to green to maintain traffic flow.
As compared to fixed time control systems, the foundation of a dynamic system is actually a detector, which is nothing more than a simple device that communicates with the traffic light and informs it about traffic conditions in real time. This time, the traffic light can not only adjust timing, but also solve traffic jams by turning red as soon as an intersection gets stuck with cars.
There are two different types of detectors, embedded into the road surface and mounted above the road.
The first ones are nothing more than simple devices using inductive loop, so they have the ability to send information to the traffic light unit when a car passes over it. This way, the traffic light which already has the power to control timing all by itself, knows for sure whether there's a queue of cars waiting for the green light or there are no cars at all, thus acting accordingly. Or simply said, if there's a car on the road, the traffic light sees it.
It's pretty easy to notice such a detector, mostly because such a technology needs small holes in the road, usually near intersections or close to crosswalks. While they are used in many regions of the world, an inductive detector loop is more expensive than all the other systems, especially because of maintenance and installation costs.
Detectors mounted on poles on the other hand are much more affordable and can be installed in the close proximity of other systems. Plus, installation is less expensive while doing exactly the same thing and sometimes even more, sending not only information regarding to the presence of vehicles on the road, but also other types of data such as real-time photos.
While all these systems are being used right now in many regions around the world, there's a city in Germany that makes us believe the future sounds good. Ingolstadt, home of German car manufacturer Audi, is currently testing what's being considered the first intelligent traffic light system in the world.
As compared to the existing solutions, the traffic lights are now controlled by the cars, so there's no need for in-pavement or above-the-road detectors to know that a car is approaching. The testing campaign started by Audi is solely focused on car efficiency, as the Germans demonstrated that this is quite an easy way to increase efficiency in crowded cities.
The whole idea is pretty simple: the vehicles communicate with the traffic lights via special equipment, mostly wireless LAN and UMTS links. Traffic lights send various information to the approaching car, including the time till the next color change, so the vehicle can either automatically adjust speed to avoid stopping or inform the driver about his options.
In addition, if a car has already stopped and is waiting at a traffic light, the on-board computer collects data such as waiting time and sends it to the traffic light which, in exchange, shows the time left until it turns green. More on the travolution project can be found here.
That being said, it's pretty clear that traffic light systems are playing a vital role in the automotive industry and although we all hate the red light, don't be so harsh on them. They're here to make roads a better place.