Ever wonder why traffic lights in downtown Tacoma takes so long to change?
Q: Why doesn't Tacoma have vehicle sensors at so many of its intersections, especially downtown? — many, many people, including some in this newsroom
A: Get ready. I got a LOT of information on this from our good friends at the city's public works department. As with most public works questions, the answer is interesting, wonky and somewhat complicated.
If you drive in Tacoma, you've probably been there: It's late at night, and you're in or around downtown, stopped at a red light. There's no one else at the intersection, yet you still have to wait for what feels like forever for the light to change because it's on a fixed timer — there's no active sensor that "sees" your car and helps you out with a quick light change.
In short, the city DOES have vehicle detection at many of its intersections, but the system is old and in need of some TLC.
Here are some facts from public works:
▪ Tacoma has 337 traffic signals.
▪ Of those, about 100 have broken or damaged "traffic loops," which detect vehicles, and which you can often see cut into the pavement.
▪ At 40 of those intersections, the bad loops have a fairly significant impact on traffic flow.
"Forty of these are really messing things up. We want to install new technology that gets us out of the ground, so we're not dealing with this anymore," said Leigh Starr, the streetlight and signal operations czar for the city of Tacoma.
The vehicle-detection system has been in place in Tacoma a long time — Starr didn't know off the top of his head exactly how long — and it's old and needs an upgrade.
Of the city's intersections, Starr said there are "about a third that are working — many of those have cameras. We have a third in the downtown core that are on fixed time on purpose, and about a third that have problems ... Ideally, we’d do it all by camera in the future, but it's expensive. So it's trying to find the resources and do a thoughtful approach."
Let's revisit that part about downtown, which is where many complaints about traffic-signal timing comes from. According to Starr, the majority of the downtown core is on a fixed-time cycle by design. Because the intersections are so close together, it makes sense for them to be run that way (think about when you're driving down the steep hills into downtown).
The Link light rail also has a huge impact on signals in that area, Starr said, because it has "hard priority" — when it comes by, the light turns green.
"We typically will change the sequencing of the signals during the time of day, so the idea is people come into the city in the morning and go out in the afternoon, so we will try to synchronize them accordingly," Starr said. "If you're a fish swimming upstream, you're never going to see synchronized signals, so if you're heading into the city in the evenings, it's going to be backward."
So, for those reasons it seems like the intersection timing around downtown is pretty set for now, though Starr said the city is hoping to make improvements in certain areas. Only 14 intersections in the whole city totally lack vehicle detection. So what about those 100 intersections in other parts of the city that have damaged or broken vehicle detection?
Some of those are getting fixed as road work and construction is done nearby, Starr said. For instance, on South 38th Street in the Lincoln District, there are several intersections where vehicle detection will be fixed once major utility work is completed.
Ultimately, Starr said public works would like to install above-ground cameras to detect vehicles at city intersections. They're expensive — per intersection, the cost is $21,000 for materials, plus a little less than a day's work to install, he said — but they wouldn't be damaged by decaying roadways and construction. The city could easily scale the project by investing the money on stretches of road that need it most.
As an example: "If you have five broken on Sixth Avenue and five broken on South 19th Street, let's just say instead of fixing three here and two there, why not fix all five on one of the corridors so you have one corridor that actually ran," he said.
This question was surprisingly timely. Starr and his team are giving a presentation on the state of the city's intersections at a City Council committee meeting May 9.
Then, in June, they'll be back in front of the committee for a more in-depth look at what it will take to improve traffic flow in Tacoma.