Traffic center adjusts signals to keep drivers moving

Traffic management center


Even though this week’s ZipMobile nightmare was the state’s responsibility, it affected city side streets with drivers scrambling to get home.

One way the city helped was by altering traffic signals.

On Tuesday, the roads looked pretty similar, almost everywhere you turned.

“I know everyone was affected both east and west, and even mauka and makai travel, but at least you noticed, when the light turned green, the traffic moved a little,” said Ty Fukumitsu, electrical engineer with Honolulu’s Transportation Services department.

At the city’s traffic management center, engineers spent about 30 hours, modifying the timing of traffic signals, trying to help the thousands of drivers who were trying to get home.

“If you didn’t change the timing of the traffic signals that day on the surface streets, traffic would have been worse?” KHON2 asked.

“Traffic would have been gridlocked, gridlocked to the point where no one is moving,” Fukumitsu said.

Traffic engineers and operators have access to about 400 intersections on island, from Kapolei to Hawaii Kai.

h1 zipperlane traffic
Previous coverage: Open ZipperLane causes traffic nightmare for westbound drivers

Fukumitsu shows us how it works:

Take Kamehameha Highway at Waimano Home Road in Pearl City. The cycle of the traffic light is programmed to change every 130 seconds, or about two minutes. In this case, there is a backlog for Ewa-bound drivers.

“We have a graphic map of the intersection that’s on the right, and on the left we have what we call traffic signal timing pages,” Fukumitsu said.

An engineer changes the cycle of the traffic signal, almost doubling it to 240 seconds, or four minutes. A few minutes after changing the timing, there are noticeably fewer vehicles than before.

“So how do you time it where you’re not backing up traffic elsewhere?” KHON2 asked.

“You’re right. The longer we keep Kamehameha Highway green, the longer the side streets have to wait, so we compensate that by giving the side streets a little extra time,” Fukumitsu said.

If there are only a few drivers waiting at traffic signals, engineers can fix that too by shortening their wait times to keep things moving.

KHON2 found out that sometimes, there are traffic engineers and operators modifying traffic signals seven days a week.

They often work on weekends to help with events like a marathon or parade, and when there are various road projects planned.

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