How Traffic Signals Keep Traffic Moving


Why Are Traffic Signals Necessary

Beyond the obvious reasoning that traffic signals preserve safety at intersections and different junctures along a roadway, traffic signals are also largely responsible for maintaining a steady flow of traffic.

Traffic signals are a necessary part of how civil engineers control and manage the pace of traffic thanks to coordination systems implemented alongside roadway design. Most people don’t think too much about their traffic light, at least not outside of disdain for catching the reds and praise for speeding through the greens.


Still, a lot of effort goes into both deciding and programing a stretch of road to ensure that the lights for both the straight and intersecting traffic can travel and move along fluidly. There is even a whole industry built around designing and improving the technology that facilitates this synchronization.

How It Works

Believe it or not, there’s an actual science to the flow of traffic in any given area. Generally speaking, a group of civil engineers and others have to sit down and figure out the timing, expected traffic capacity, and a whole range of other factors before a stretch of road will function efficiently.

Going back to the experience of hitting all the reds, or sailing through the greens, there’s an actual phenomenon that refers to that exact experience. Called a “green wave”, there are moments when drivers can move through a series of lights without having to stop. In terms of traffic control and driver satisfaction, this is a pretty ideal situation as it prevents traffic from building up, which can complicate all other intersecting pathways.

Of course, “green wave breakdown” as it’s called in the article above, is what happens when something prevents that steady stream of movement. It can happen for all kinds of reasons, including things like poorly programed traffic signals to an excess of traffic being diverted to an area that’s usually programed for other numbers. Maybe there was an accident offsetting an intersection and changing the traffic patterns. 

As the article suggests, green waves are beneficial because they essentially reduce traffic, which can be beneficial for the environment, further traffic loads, and improved pedestrian and cyclist safety. As most roadways are designed to accommodate this experience, you can rightfully imagine that when it breaks down it tends to complicate the whole system.


Key Factors

There are a few key factors in maintaining the orderly flow of traffic and preserving these green wave experiences. While each plays its own role, the system essentially relies on every piece functioning at its highest level of efficiency.

  • Synchronization vs Coordination

One of the first things to consider is the style of coordination. Synchronized lights are a lot like synchronized swimmers, they move and change at the same time to create a long corridor of green lights. In most cases, this isn’t ideal because it doesn’t account for intersections and a higher load of traffic. While in instances where very few cars make use of the road in question, such as more rural roads or places outside of heavily trafficked areas, it may offer a quicker drive. 

The other side of the coin is coordinated signal change, which is a series of changes designed to let traffic move through in packs. Typically, this works better for areas with a lot of traffic, but it’s still susceptible to a breakdown based on unexpected changes to whatever formula is used to calculate the light timing.

  • Traffic Signal Technology

The next major component is the technology used for the signals themselves. For anyone driving or walking along the road, warning signals provide vital information about your travel environment. For drivers in particular, the main interactive component is usually the traffic light. Red, yellow, green, just like we all know and love, or red, green, yellow, and “I swear it was still yellow”. But there’s a lot more at play in modern traffic signals than just the lights. 

Intricate radio and connective devices called controllers are often linked to streetlights in order to communicate both with surrounding streetlights and related technology. While this allows for a more full picture of an area’s traffic situation through precise control and programming, it also means that each piece of equipment is responsible for its role in holding together the puzzle.

  • Road Design and Metrics

The final major component is the road itself. Oftentimes roads are built out of necessity or civic expansion. As cities and towns grow, they need more roads to get to newly developed areas. When this happens, in most cases, it’s important to understand what kind of environment that road is expected to facilitate and endure. What that means is that whoever builds and designs the roads has to consider all the factors that will influence traffic making use of that space.

Think of your local highway. How many people live in your city, and how many people are likely to use that highway to get to work, drive home, go to the store, etc.? Now, what would that road look like if one of the exits is blocked by an accident, or if a highway was closed for repairs leaving the one in question as the only viable route to some heavily populated part of the city?

Could the first highway support that? These are only a few of the questions that people have to think about when constructing new roads, and that’s barely considering the interaction it will have with all of the preexisting roadways that may need to be adjusted to account for changes. Traffic signals will need to be added accordingly as well, and due to the expense and time intensive nature of adding new infrastructure, these decisions all have to take into account not just the past and present of an area, but the potential growth and change that might influence the roads as well. 

So, Why Traffic Signals

Traffic signals are, for the majority of people, the most important part of that equation. The reason is simple, it’s the part most people will actually see and interact with. In an ideal situation, every other part of this equation would be invisible to the average driver. A working traffic space that’s been engineered well and maintained should provide drivers and pedestrians alike with a reasonable satisfactory and forgettable traffic experience.

With traffic signals playing such a significant role, it’s important that the tech evolves to match the capacity and requirements of any project that calls for them. As part of our continuous effort to support the safety and speed of all roadways, ELTEC continues to develop newer and safer traffic technology.