Not only are Seattle area freeway trips getting slower, they’ve also been highly unpredictable lately, as this three-year chart by bus commuter Tim Ellis shows.

Ellis rides the Sound Transit 510 bus, and he plotted weekday trip times from the I-5 Broadway Avenue onramp (two minutes south of Everett Station) to the I-5 Stewart Street exit in Seattle.

He found that in the month ending Nov. 3, his average bus trip took 65 minutes, approximately 10 minutes longer than a year ago.  Read our related story here, about how Community Transit and Sound Transit just added a few buses to relieve overcrowding.

Of special importance in Ellis’ chart are the blue dots at the upper right — they show five days this fall when passengers sat or stood on the 510 bus more than 90 minutes.

 

Traffic delays are causing people to crowd into an earlier bus, so they can arrive on time, transit officials say.  Ellis says that while more bus capacity is good, the agencies lack “infinite money” to do more, and this week’s new runs tackle only part of the problem.  “The park-and-rides are full,” said Ellis, founder of the Seattle Bubble real-estate blog. “At 7:30, the buses were half empty, because people had gotten onto the bus earlier.”

And here’s another chart showing traffic delays getting longer in the general traffic lanes, from data that WSDOT provided to Community Transit. The average car trip increased to 75 minutes by late October.