America needs a hero, and though Mats Järlström hails from Sweden, he might be it. He won't reverse climate change or close the wealth gap, but he may help unmake another injustice: that of the ticket-slinging red light camera.
Järlström waded into this fight in May 2013, when authorities ticketed his wife, Laurie, after a camera recorded her turning through a red light in Beaverton, Oregon, where they live. Järlström, who earned a degree in electrical engineering from Sweden’s Ebersteinska gymnasium in 1980, but now works on audio products, saw more than an annoyance. He saw a math problem, one that might reveal whether the traffic signal gave his wife enough time to safely stop before the light turned from yellow to red.
He claims it did not, that Laurie didn't deserve the ticket, and that Beaverton didn't deserve her money. If correct, his argument calls into question at least some of the red light cameras monitoring intersections nationwide, because the same flawed traffic signal timing that caught Laurie Järlström could be trapping others, and handing out unfair tickets as a result.
To explain Järlström’s work and why you're hearing about it now, I must take you on a quick journey through the science of traffic light timing. Traffic engineers’ goal is to keep everyone safe but moving as efficiently as possible, so they rely on a time-tested signal formula that accounts for factors like speed limit, road surface, and how quickly humans can react to a changing light. The result dictates how long a light stays yellow before turning red, typically three to five seconds. (Red light camera manufacturers, it should be noted, have nothing to do with this formula.)
The goal is to minimize the likelihood of drivers finding themselves in the "dilemma zone," where it’s too late to stop safely, and too late to proceed without running the light---and possibly getting a ticket.
Wouldn't a longer yellow light solve all these problems, you say, to which I say, not necessarily! Humans are tricksy, adaptable things, and if local drivers catch on to the longer yellow, they might power through it with more gusto. Efficiency-minded engineers also argue that long yellow signals are a waste of valuable seconds, because neither side of the intersection is really moving when they're illuminated.
So this dilemma zone has been the subject of study for decades, with psychologists and engineers banding together to understand the vagaries of human perception and reaction time. The formula engineers use to time lights right now, however, dates to 1960, based on the work of three General Motors physicists. The Institute for Transportation Engineers (ITE), the industry’s premier professional organization, still recommends their formula as a best practice.
It’s impossible to say how many places use the equation to time their lights---each state and locality sets its own rules---but it’s certainly used widely, not least because engineers are a risk-averse bunch who don't like getting sued. “Most traffic engineers tend to stick with ITE practices just because they don’t want to go into court and say they’ve done something different,” says Anuj Sharma, a traffic safety researcher at Iowa State University.
Järlström isn't the only one who says the equation is flawed. “This formula, which we derived, cannot be applied to turning lanes or to any situation where the driver must decelerate within the critical distance,” Alexei Maradudin, the only surviving physicist of the three who created it, wrote in a 2015 letter to the ITE.
Maradudin says they designed the formula to determine the time needed for drivers going straight, and the result might not leave enough time for those who, like Laurie Järlström, must slow down a bit as they execute a turn. (Maradudin declined to comment for this article. “I hope that you will understand that I am not very interested in discussing work I did nearly 60 years ago,” he said.)
The dilemma zone, in other words, might look a bit different for turning drivers. Maybe they deserve a longer yellow---not a ticket for a violation they couldn't avoid.
OK! Back to Beaverton. After Laurie Järlström received her ticket for running a light back in 2013, her husband recorded a video of the traffic signal in question and analyzed it frame-by-frame, stopwatch in hand. He discovered, first, that the yellow signal was 0.3 seconds shorter than Beaverton authorities claimed it to be. But he also found the same formula flaws Maradudin suggested---that a driver in the turning lane who hits a yellow might not have enough time to notice, react, and navigate safely out the intersection before the light turns red. They’re stuck in the dilemma zone, he alleges, with no good options.
Järlström emailed this information to Oregon’s Board of Examiners for Engineering and Land Surveying in 2014, and that’s when things got ugly. According to a lawsuit Järlström filed last week, the board responded by opening an investigation into the Beaverton resident. He had improperly identified himself as an “engineer’ when he has no license to practice in Oregon, the board said, and fined him $500 in 2016 after a two-year investigation. This infringes on his first amendment rights, Järlström says. “I want to be able to describe myself as who I am, to be able to talk about myself freely,” he says.
None of that speaks to the validity of his findings, of course. According to Hesham Rakha, a Virginia Tech Transportation Institute engineer, Järlström’s works makes some assumptions about human behavior. But he and other researchers have found similar flaws in the recommended traffic light timing.
In a 2012 study, Rakha's research team found that drivers who hit yellow lights designed according to that ITE formula will be trapped in that pesky dilemma zone as much as 15 percent of the time. The team has also found the current signal timing formula doesn’t sufficiently account for longer vehicles like trucksand buses, or for very wet weather. “Based on our study, there are people getting tickets for the wrong reasons,” Rakha says. “They were in the dilemma zone. They had no choice.”
So, does this mean municipalities all over the country are collecting millions in traffic violations from drivers who run red lights when there’s no other safe choice? Maybe. More and more cities have adopted these cameras over the past two decades, but there's little aggregated public data on the resulting tickets.
Aggrieved drivers, however, have cause for hope. Before long, connected infrastructure could warn drivers of imminent light changes and advise them whether to stop or go through the intersection, helping them avoid the dilemma zone altogether. (Audi already offers tech like this in its latest model.) In the meantime, the Institute for Transportation Engineers is in the midst of a long, peer-reviewed process to update its traffic signal timing guidelines. It should wrap up in the fall, and is including Järlström's criticisms in its process. “ITE is always open to receiving comments and new research knowledge as part of the development process for our recommended practices,” says Douglas Noble, who heads up operations at the organization.
Can you hear the folk song yet, the one against the man who fought the traffic lights and won?
