Q: What intersection in Tacoma has the traffic signal with the longest red light?
A: Simple question, that, and we put it to Joshua Diekmann, city traffic engineer and go-to source for us here at Traffic Q&A headquarters.
The answer, it turns out, is a bit complicated.
“Generally, the locations with the largest delays are the biggest and busiest intersections,” Diekmann told us. “Since the longest red time varies by day depending on traffic conditions, the information I have provided below is an estimate of the average delay based on our most recent traffic count data.
“If all vehicles and all directions at an intersection are considered, the following five locations have the highest average delay per vehicle during the evening peak hours:”
Drum roll, please ...
▪ South 19th Street and Sprague Avenue, 2 minutes, 35 seconds.
▪ Sixth Avenue and Sprague, 2 minutes, 20 seconds.
▪ Marine View Drive (state Route 509) and Taylor Way, 1 minute, 20 seconds.
▪ South 19th Street and Pearl, 1 minute, 10 seconds.
▪ St. Helens/Tacoma Avenue and Division, 1 minute, 5 seconds.
Wait, 19th and Sprague?
Our guess would have been Sixth and Sprague, where a tangle of streets comes together in a nightmare of indecision, especially when it comes to making a right turn from northbound Sprague onto any of those cross streets. *shudder*
Diekmann feels our pain.
“Sixth and Sprague ... is a large five-way intersection, and vehicles and pedestrians have longer crossing distances,” he said. “Due to the complicated geometry of the five legs, only one direction can go at a time, which increases the wait time for all directions.”
What pushes 19th and Sprague to the top of the list is sheer volume.
The city estimates that as many as 4,100 vehicles traverse that crossroads during the evening peak. We are often among them, as TQA HQ is mere blocks away, and we have chafed at the wait, longing as we do to leave the salt mine in the rear-view mirror, especially on a Friday.
While it’s not in the Top 5 for average delay, an intersection where waits can be long is Route 509 and Alexander Avenue out on the Tideflats.
“At this location, wait times for northbound and southbound vehicles on Alexander Avenue are higher than at other locations in the city because the total number of vehicles on these approaches is much lower than the total number of vehicles on SR 509, so the majority of the signal green time is given to SR 509,” Diekmann said. “While this reduces the overall delay for most vehicles, wait times for vehicles on Alexander are higher than at most other locations.
Relief there might be in sight.
“The state is planning on rebuilding this intersection with the upcoming SR 167 completion project, and is in the process of designing these improvements,” Diekmann said.
Engineers monitor the 335 signalized intersections in the city and strive to make improvements, he added.
“... the city’s Public Works Department already has projects scheduled at many of the city’s busiest intersections and is making plans to continue upgrading signals throughout the city to improve the safety and performance of our intersections for all users,” Diekmann said.
That includes at the Top 5 listed above.
“Each of these locations has a project underway or planned to begin within the next year,” Diekmann said. “Improvements at all five locations are expected to be completed within the next three years.”