Seattle-Tacoma Traffic Among Most Unpredictable in Nation—How Does Your Commute Compare?

Heavy traffic is nothing new in the Puget Sound area, but a new study shows the severity of our rush-hour jams is especially tough to predict.

The latest Urban Mobility Report, released today by the Texas A&M Transportation Institute, shows drivers in the Seattle metro area, which includes King, Pierce and Snohomish counties, spent an average of 48 hours—two whole days—sitting in traffic in 2011.

That figure ties Seattle-Tacoma with Philadelphia for ninth-place among the country's 15 largest metro areas when it comes to average hours lost to traffic congestion.

According to the Washington State Department of Transportation's 2012 Congestion Report, the longest duration of congestion (defined as time when average speeds are below 45 mph) on major Puget Sound area freeways for the morning commute can be found in northbound I-405 between Tukwila and Bellevue. Commuters in 2011 withstood three hours and 30 minutes on this stretch of road. This same stretch, headed southbound was also the longest congested for the afternoon commute at four hours and 45 minutes. (View the report on pages 30-31 for major roadways you take for your daily commute: http://wsdot.wa.gov/publications/fulltext/graynotebook/CR12.pdf)

Data for roadways closer to Enumclaw were not immediately available though historical collision data for State Route 164, State Route 169 and State Route 410 might hint at where bottlenecks are most likely to occur closer to home. According to a WSDOT collision report from June 2010, State Route 410 at Watson Street North averaged the highest number of collisions between 2003 and 2007.

State Route 164 between 216th Avenue S.E. and Lafromboise Street, and State Route 169 south of S.E. 416th Street were also identified as areas with higher-than average collisions between 2002 and 2004.

Heavy and Unpredictable

But another aspect of the Texas A&M Transportation Institute study shows our region's traffic isn't just heavy—it's also highly unpredictable.

For the first time, researchers also measured the amount of a time a driver must plan to ensure on-time arrival 19 out of 20 times. Seattle-Tacoma's "Freeway Planning Time Index" came in at 3.99, meaning commuters must set aside 80 minutes to consistently arrive on time when traveling on a route that takes 20 minutes in light or no traffic.

The figure puts traffic in Seattle-Tacoma at 12th most-unreliable out of 101 urban areas across the country. Despite a significantly smaller population, nearby Portland actually scored higher than Seattle-Tacoma, with an index of 4.26.

Congestion in our region got slightly worse in 2011, according to the study, with the average number of hours lost in traffic increasing from 47 to 48. But these figures are markedly lower than 2006, when the average was 54 hours.

How much time do you set aside for your daily commute? Tell us in the comments section.