Do you have a least favorite traffic light? I'd be willing to bet that most people who drive daily in Iowa have a light at which they hate getting stuck.

I don't think this problem is specific to Iowa either but there is nothing worse than approaching a traffic light you know takes forever to turn green, and as you're 100 yards away, you watch the light change from yellow to red. Usually, the busier the intersection, and depending on if you're making a left turn or going straight, the longer you'll have to wait.

I have a light near my house that whenever I have to make a right turn, it's pretty easy to get through but if you're going straight or have to turn left and you catch the start of a red light, if it's before 6 am, you're going to be sitting there for what feels like forever.

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I found this article from the Gazette that did some digging on traffic lights in Cedar Rapids and how they are timed. This might not be exactly how it works for every town in Iowa but it could give us some insight on how/why Iowa traffic lights work the way they do.

How Do Lights Know Cars Are at an Intersection

Cari Pauli is the Cedar Rapids City Traffic Engineer and she said there are plenty of factors that play into how traffic lights are timed. It can depend on the time of the day, the number of vehicles on the road, what type of intersection the lights are being used at, and if there are pedestrians at the intersection.

Where people may start to get impatient or upset is when you are sitting at a stop light that never seems to change to green. You might try rolling forward or backward to get the light to change but supposedly that might not help very much. Cari told the Gazette it's best to pull up to the stop bar and don't move. Some signals have cameras to detect cars at intersections but most use loop detectors that are wired into the pavement.

"If a vehicle is stopped too far back from the stop bar or too far beyond the stop bar, they may risk not being detected. [The loop detector] It resonates at a particular frequency and when a vehicle traverses the loop, it increases the frequency and sends a signal to the controller that says a vehicle is present."

How Long Does it Take for Lights to Cycle Through Colors?

In Cedar Rapids, how fast traffic lights cycle from red to yellow, and green can change based on the time of the day. Cari explained why these cycles are longer and shorter.

"You might run a cycle length of 90 seconds in the morning, but then when it drops off at 9 o’clock, we might run a 70-second cycle length because there isn’t as much traffic and we want it to be really efficient. And so then we don’t have a longer cycling to make people sit and wait on the side streets longer."

The Cedar Rapids traffic signals usually will have their timings reset every 3 years as the 175 Cedar Rapids lights are all upgraded/updated on a rotating schedule. When lights are updated, they aren't just choosing times at random either. Data is pulled to try and help improve the process on when certain timings work best.

Are All Iowa Traffic Lights the Same

Not every city will use the same methods to improve their traffic lights but for the most part, cities use the same practices. For example, Cedar Rapids traffic lights will have a brief moment where all the lights at an intersection are red before cycling through a change.

Not all cities use this method but according to Cari, most cities do use a standard practice with their intersections. One of the best things you can do if you believe there is a traffic light that isn't functioning how they are supposed to or you believe the loop wire is off, the timing is wrong, etc, you can call your traffic engineering team with your cities department of public works. Cari told the Gazette

"If a person says ‘Hey, I was at the intersection of First Avenue and Sixth Street and I sat there for four cycles and I was there at 4:55,’ we can go back and look. Based on what is found, adjustments can be made."

If there is a light you think takes too long to cycle through the colors or you believe the loop detector doesn't do a great job of detecting your vehicle, it might be worth calling your public works department to see if they can take a look at that intersection.