Why do the traffic lights take so long to change after the Link comes through?

Question: What is the logic behind the timing of the lights on Commerce Street when the Link light rail is running? — John G., Tacoma

Answer: Anyone who’s tried to go east and west through downtown Tacoma certainly understands the plight at the light.

But for those of you who don’t, John goes on:

“I understand making the light red for the cross streets so Link doesn’t have to stop all the time, but I do not understand why the lights stay red for so long.

“The other day I was going up 13th and had to stop for Link, even though it was not in sight when I turned onto 13th. I was the second car in line, and when I finally got to cross the street, I looked down Commerce and saw that Link was well past 11th, closer to Ninth.

“It would eliminate a lot of wait time and frustration if the lights turned green a lot sooner after the Link goes through an intersection.”

Yes, yes it would. So I took this to Josh Diekmann, city of Tacoma traffic engineer.

“Signal timing along the existing Link alignment is constrained by the fact that portions of the alignment only have one set of tracks,” Diekmann says. “In these locations, the signal remains red for an extended period in order to allow trains traveling in the opposite direction to pass each other, or, in the case of Commerce Street, the light remains red while trains traveling in the direction opposite traffic clear the intersection.”

The city maintains the signal timing through the Link’s current alignment and through where the Hilltop extension will be installed, and will do so for the expansion of the system that will come with Sound Transit 3.

Sound Transit works with the city to help develop signal-timing strategies, Diekmann says, especially when the agency has to change the Link’s schedule.

However, some good news is coming down the tracks for you, John.

Once a second set of tracks is added to the Link line along Commerce Street as part of the Hilltop extension, wait times at the traffic lights should shorten considerably, Diekmann says.

Is there something you’d like to know about construction projects or the rules of the road? Send your questions to, call 253-597-8627 or tweet to @KennyOcker on Twitter.