A repurposed toy car runs on a tiny model of McCarran Boulevard in Dr. Zong Tian’s lab.
A repurposed toy car runs on a tiny model of McCarran Boulevard in Dr. Zong Tian’s lab.

Have you ever sat at a traffic light and wondered who set the timing that determines when it’s your turn to go? Dr. Zong Tian is one of those people.

Originally from China, Tian is a traffic engineer, and he’s been working with government agencies to help time some of the Truckee Meadows’ traffic signals since moving here to teach at the University of Nevada, Reno in 2004.

Recently, Tian developed a new teaching tool. The Physical Arterial Signal Simulator—PASS for short—is a system that uses computer simulations, real traffic timing equipment and a tiny model of a busy stretch of McCarran Boulevard to teach traffic engineering students how to time signals.

“You can play here—’OK, let me try this and this. How is it going to affect the traffic?’—and then once you feel comfortable, and you go to the field and see exactly the same thing, then you feel a lot more comfortable,” Tian said during a recent interview in his lab on the UNR campus.

Phased in

Tian didn’t get his start in signal timing until years after coming to the United States for graduate studies. In China, he studied railroad engineering.

“When I got here, there are no railroads, really,” Tian said. “Railroads are not major here. But I wanted to study, to continue with transportation. I enrolled in a graduate program at the University of Idaho. When I was working on my first research project, it was not about traffic signals.”

It was about stop signs. In fact, Tian didn’t begin working on traffic signal timing projects until he’d completed his master’s and got his first job at a consulting company.

“I just fell and fell in love,” he said. “I thought, ‘This is something I want to do. I know it has theory. It has models. It has electronics. It’s a combination of different things.’ That’s when I started to get interested in traffic signal timing.”

He went to Texas A&M University for a PhD before making a move to Reno to take up a professorship at UNR.

“When I came to Reno, the first thing that I saw was the signals near UNR,” Tian said. “I said, ‘These signals, I think, can be better controlled—better operated.’ I wrote a proposal to NDOT, and they supported me. They gave me a grant.”

It was more than a decade ago when Tian retimed the traffic signals near UNR on Center, Virginia, Sierra, Eighth and Maple Streets. And today, he and a small team of graduate students do the same for traffic lights around the Truckee Meadows.

Dr. Zong Tian inputs information into a traffic signal controller.


“That’s the work actually we are helping with,” he said. “We are the main player to help the local agencies to time those signals. Before, they used to hire companies from outside, like California. And they’d come here for a day. They’re not really familiar with the locations or the situation. The signals never really worked.”

Tian said he and his students work with the RTC and the cities of Sparks and Reno. His students spend time in the field, gathering data about intersections and crosswalks before developing and implementing timing plans. A few months ago, they began doing this with the aid of Tian’s new PASS system.

Timing is everything

Traffic signal timing is a pretty complex task—and a person lacking the engineering background could get bogged down in information while trying to understand Tian’s PASS system.

A database runs simulations, transmitted between a computer and real traffic timing equipment—called controllers—in the lab. It allows Tian and his students to manipulate a host of variables at work on the intersections along any stretch of road. They control for things like phase—how long and in what order lanes get a green light—and cycle length, the amount of time it takes for all of the lanes at an intersection to get a green.

Demonstrating his system, Tian reiterated that it’s designed as a teaching tool to introduce the principles of traffic engineering. “For people like you—who don’t have any traffic engineering background—I can show, ‘Here is a good timing. Let’s watch it. Here’s a bad timing. Let’s watch it,’” he said. “And you’ll see how the cars go.”

But it gets a lot more complicated than that. Tian’s PASS system is also meant to teach students about pedestrian signal systems and sensors—cameras and electrically conductive loops embedded in the pavement—that detect cars at intersections. These things are all built into the tiny model that’s part of the PASS system.

It’s a model of McCarran Boulevard between Clear Acre and Northtowne Lanes and includes those intersections plus the two for north- and southbound 395 between. A repurposed toy car runs along the roadway while the traffic signals change based upon a timing sequence transmitted from the computer to the traffic controllers attached to the model.

But the model isn’t functioning properly. Not all of the tiny pedestrian signals send out a call when pressed. The toy car with its cabin stuffed full of electrical components goes too fast. And sometimes it doesn’t stop.

Tian intends to get it fixed but said that’s going to be a bit of a process.

“Actually, I built this in China,” he said. “It’s just impossible to build this here. It’s too expensive. You think about it—’Here’s my idea. Build something for me.’ I don’t even know where to find this kind of company.”

Tian had a friend in China who also works in the transportation field but has a background in electrical engineering. He asked for her help getting the PASS system built and shipped to the U.S.

“The ship from China took a month, but apparently something got damaged,” he said. “We’ve tried to fix everything, but, still, some things are not working.”

He’s waiting for someone from the Chinese company that built the model to travel to Reno to fix it. He expects that to happen before the end of the year. In the meantime, he and his team of grad students are continuing to retime lights around the valley—including, recently, at the intersection at Interstate-80 and Keystone Avenue.

“We just retimed that,” he said. “You should drive there to see it, to see what you think.” If you want to see what you think and report back on it, the RTC has a number you can call: 335-7623. According to the RTC website, “When a report is called in, the appropriate local government that operates and maintains the specific signal will be contacted.”

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