Drivers know it. The state confirms it. Rush-hour commutes on Puget Sound's highways are taking longer and longer. The biggest increase in...

Drivers know it. The state confirms it.

Rush-hour commutes on Puget Sound’s highways are taking longer and longer.

The biggest increase in drive time: Bellevue to Federal Way via Interstate 405 and I-5, 14 minutes longer than two years ago. That commute is 56 minutes on average during peak commute times.

The state Department of Transportation on Friday issued its latest summary of average commuting travel times on area freeways, based on data taken from 2004 to 2006.

The increased times ranged from four to 14 minutes. Among the increases, Everett to Seattle and Bellevue to Tukwila each grew seven minutes longer; Seattle to Bellevue, via Highway 520, five minutes longer.

The slowest average speed during a peak commute, according to DOT, is 23 mph from Tukwila to Bellevue along I-405.

Information

For current travel times: www.wsdot.wa.gov/traffic/seattle/traveltimes

“These numbers confirm what drivers already know,” said Martin Dedinsky, DOT traffic engineer who compiled the figures. “Congestion is increasing, commute times are increasing and the definition of rush hour is spreading on both sides of the day.”

The department attributed the increased commute times to job growth, additional cars and not adding more roads or mass transit. Road construction was not an issue in the increased times, according to DOT.

“Several factors are playing a part in the buildup of congestion,” said Doug MacDonald, state transportation secretary. “In the period from 2003 to 2005, the Central Puget Sound region added more than 40,000 new jobs and more than 70,000 new people. Growth is placing ever-greater demands on the system.”

The new information also serves to verify numbers reported in November in a congestion report.

The November report, for example, calculated how long various freeways are clogged. A freeway is considered congested if average speeds are slower than 40 mph. At the time, the report found that, under that standard, evening congestion on southbound I-405 lasted an average of five hours, 35 minutes in 2005.

Aside from doing those calculations, the DOT also is able to figure average speeds; in fact, those average-speed calculations have become one tool available to drivers to help them endure the torture of commuting, with the average drive times at any particular moment available on a DOT Internet site and commonly streamed across the bottom of TV screens during rush-hour driving.

All calculations use similar techniques: information provided by roadway detectors and other data to calculate numbers of vehicles, volumes and peak commute times.

The recent reports use information from different periods, however, with the November figures based on 2003-to-2005 data and the average-travel-time calculations based on numbers from 2004 to 2006.

The latter figures found that travel times increased at peak periods, speeds slowed, peak congestion times lengthened and the reliability of travel times worsened.

But while the technology and calculations have improved, the message is the same: Driving is turning into a syrupy descent into arterial failure.

In March 1997, a DOT study predicted that average I-405 commuting speeds would fall to 26 mph — but expected it would take 20 years to reach that point.

Instead, the corridor reached the 23 mph average in less than 10 years.

Jamie Holter, DOT spokeswoman, chuckled wryly about the decade-old prediction.

“That’s exactly it,” she said. “It’s simply not getting better.”

Peyton Whitely: 206-464-2259 or pwhitely@seattletimes.com.