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FAQ City: How To Get A Poorly-Timed Traffic Light Fixed

Open Grid Scheduler / Flickr
How do Charlotte's traffic signals work? And what should residents do if one is causing backups?

We all know the feeling. You're in a rush on your way to work or to drop the kids off, and you end up hitting back-to-back-to-back red lights. Your blood pressure kicks up, your body tenses, and your brain screams LET'S GO! Turn green already!

It's more than just an everyday annoyance. Excessive red lights cost drivers time and gas, and can encourage risky driving habits - like speeding to make the next light.

WFAE listener Christine Thomas says she hits a string of red lights nearly every day on her morning commute down Mint Street in uptown Charlotte.

"Some days I literally come to a stop at every single traffic light, which is kind of annoying," she told us.

She wanted to know if Charlotte has a traffic-timing system in place, and if so, why does she hit so many red lights on Mint Street, and could the city better coordinate them to keep traffic flowing?

In order to find out, we reached out to Charlotte's transportation systems manager, Nathan Conard, who told us there are a few things to look for when determining if a traffic signal is malfunctioning, or perhaps functioning correctly but inefficiently.

The Three Types Of Signals

The first step is to figure out what type of traffic signal you're dealing with. According to Conard, there are three possibilities:

  • Wire (Inductor) Loop - At these intersections, thin wires have been embedded in the pavement, usually in a rectangular shape. They sense when metal passes overhead (like a car) and tell the traffic light to stay green until all the cars have passed, or until the light maxes out on time. Of Charlotte's 840 traffic signals, about 60% are on a wire loop. Among their problems - they can't always detect motorcycles or bicycles, and can struggle to detect traffic if the pavement deteriorates or becomes uneven.

  • Camera Controlled - Ever seen a video camera perched above or near a traffic light? It's not a red light camera (Charlotte scrapped those in 2006); it's there to help the traffic signal. It works just the same as a wire loop, but the cameras visually detect vehicles and instruct the light to stay green until the lane is clear. About 40% of the city's traffic lights are camera equipped. Generally they work well, but can have issues with fog, glare from the sun, and low-light conditions.

  • Fixed Loop - The third type of traffic light is not controlled by cameras or wires, but instead runs on a timer with a preset loop. These only make up about 10% of the city's traffic lights.

Time of Day

If you've determined the type of traffic signal you're getting stuck out, and you can safely say it's not because of a faulty wire or camera, the next thing to consider is the time of day you're driving.

Conard, the traffic manager, says nearly every traffic signal in Charlotte runs on four pre-determined traffic patterns: morning rush, midday, afternoon rush, and overnight.

Sometimes, when the lights are switching from one pattern to the next, they get out-of-sync.

"Sometimes it's really quick," Conard says, "Sometimes it's less than a cycle. But sometimes it takes a couple cycles for the intersections to get back in sync with each other."

Are you hitting a lot of red lights at 6 a.m.? The intersections might be transitioning from overnight to morning rush, and you're driving at the exact wrong time.

If Nothing Else ...

In Christine's case, a test drive down Mint Street during the 7 a.m. morning rush turned up a mixed bag of evidence. Only two of the six intersections had cameras, and none appeared to have wire loops.

Credit Courtesy
Christine Thomas and her dog, Reggie

The skies were sunny and clear, ruling out the possibility that the cameras couldn't see well, and the traffic lights had already switched from overnight to morning rush about an hour before Christine buckled her seatbelt and put the car in gear.

So if equipment and time of day aren't the problem, then the issue is likely with the preset traffic pattern.

Getting those patterns right is a major part of a traffic engineer's job, and one of the most difficult. In a perfect world everyone would always get a green light, but that can't always happen, and especially not in areas with lots of criss-crossing streets.

"We're not always going to be able to progress every direction of every street," Conard says, "and that's beyond signal timing. That's just physics."

Improving Traffic Flow

That said, there are opportunities to make things better. The city could invest in more cameras and wires at those uptown intersections, and engineers can always work on fine tuning their traffic patterns.

But the city won't fix what it doesn't know is broken.

Conard says the best way for residents like Christine to alert the city of a frustrating series of traffic signals is to dial 311, press 5 for "other city services," and let the operator know what intersection is causing problems and the time of day they're driving.

Residents can also submit requests for traffic signal "timing evaluations" on the Charlotte Department of Transportation's website.

The DOT has people reviewing every complaint, and if an intersection has a particularly bad rep, they'll send an engineer out to investigate.

Even if no one calls in to complain, every intersection get retimed - no matter what - every two years. The DOT says that's to keep up with Charlotte's growing population and its ever changing traffic patterns.

So even if things are bad right now, hold out hope! The intersections may improve in the next retiming.

Do you have a question you'd like us to investigate on FAQ City? Get in touch! Questions can be about anything, as long as they relate to Charlotte or the surrounding region. Send us your question in the box below and we may follow up!

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Nick de la Canal is the host of Weekend Edition on Saturday/Sunday mornings, and a reporter covering breaking news, arts and culture, and general assignment stories. His work frequently appears on air and online. Periodically, he tweets: @nickdelacanal