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UW meteorologist takes the temperature of Seattle traffic

One crash can jam up traffic for hours around Seattle. (WSDOT)

He’s usually sought out for his meteorological insights on Seattle-area weather. But Cliff Mass has turned his data-driven lens to take the temperature of another local interest — Seattle traffic.

Related: Will this new ramp ease congestion through Tacoma?

The University of Washington meteorologist usually writes about weather on his blog, but he recently jumped lanes to weigh in on Seattle’s infamous traffic woes. Why is a weather expert so concerned about Seattle traffic?

“I care about global warming and traffic is very wasteful of fuel and thus contributes to climate change,” Mass said.

“I am increasingly getting caught in regional traffic jams,” he said. “The traffic changes the way I work.”

For example, bad traffic influences scheduled meetings for the local American Meteorological Society that Mass attends.

There are many causes for the region’s bad traffic, but Mass breaks it down into one main argument: Seattle traffic is made worse because of poorly planned arterial routes and other issues around the main paths of freeways and highways. There’s just no capacity to accommodate a rush of traffic.

Cliff Mass vs. Seattle traffic

So what contributes to this lack of arterial capacity, or other reasons Seattle roads are clogging up? Here are a few highlights from Mass’ post.

Road diets

Road diets reduce roads to fewer lanes. Mass points out projects on Rainier Avenue or NE 125th Street, where four-lane roads were often converted into two lanes, with a center turn lane, and bike lanes on each side. Traffic and pedestrian accidents do go down in such cases as drivers are forced to slow down, he argues, but so do commute times.

I could go through the other Seattle road diets with you using google maps, but the conclusions are the same: dieting has promoted congestion and substantially reduces maximum throughput of the road. Just as small blood vessels can assistant (sic) blood flow when major arteries feeding the heart are clogged, preventing a heart attack, road arterials with excess capacity stand ready to take over some of the traffic load when major roadways (like I-5) get clogged. And Seattle is deliberately reducing this valuable resilience. A big mistake.

Seattle Mayor Ed Murray, however, has argued otherwise. He recently said that traffic improvements on Rainier Avenue, where Mass points to a road diet, have cut down on accidents while also improving commute times by 3 minutes during peak periods.

But the smaller-capacity roads cannot take on heavy loads when there are incidents elsewhere. Take the recent butane truck crash, for example. The truck turned over on I-5 in February, halting traffic in all directions on the freeway. Traffic was diverted to city streets which stalled under the pressure. Seattle was brought to a near standstill. And who can forget the infamous fish truck fiasco, or even crabpocalypse.

Sounder trains and light rail

While many who complain about Seattle traffic may also complain about paying for rail service, Mass argues that the current rail service needs to be expanded and improved. The Sounder Train, for example, runs on a far too limited schedule. There needs to be increased service, he writes. He also said that the system needs better PR; combined with better reliability (cleaning up mudslides faster) more people would likely take the trains.

Light rail is also on Mass’ list. He notes that there is increased ridership on the light rail system, but also points out that parking at stations is not sufficient. He writes changes should be made so light rail is competing less with street traffic.


Bridges open too much for boat traffic, according to Mass. While the bridges do not open during commute times, Mass argues those time frames are from 7-9 a.m. and 4-6 p.m. — far too narrow of a span.

… Seattle commute time extends way beyond that in Seattle (more like 3-7 PM) and traffic is heavy outside of the commute period as well. These bridges open a lot–5500 times in 2016 for the Fremont Bridge, for example. Often a bridge opens for a single sailboat. Does it seem reasonable to mess up traffic for 15 minutes or more and inconvenience hundreds of people (or more) for the sake of pleasure sailing? I don’t think so. For the University Bridge, the traffic sometimes extends 1/2 mile north to University Village.

Mass waxes on about more than just these three points. There are also distracted drivers causing accidents. And then there are bike lanes to be considered — they need more support and maintenance.

“I commute by bicycle and the conditions are very poor, and no one seems to care,” Mass said. “It seems to be another example of ineffective local government.”

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