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On ‘Congestion Ahead’ signs, cut-through traffic, and speed limits

Reader board warning of congestion on westbound Hwy 26 just before the Sylvan exit. (Photo: Lisa Caballero/BikePortland)

I don’t have much reason to drive on Highway 26 anymore, now that I no longer have a dog who requires regular grooming. So I can’t tell you how long Oregon Department of Transportation’s reader board has been warning about congestion. But happily for drivers, the warning is actionable. If you are heading downtown, it is placed just before the Sylvan exit. What fool wouldn’t cut through local streets to avoid back-up at the tunnel?

ODOT installed its first Dynamic Message Signs (DMS) less than a decade ago after studying how the technology worked in other cities. What they learned was that the reader boards significantly reduced the number of crashes in those cities, and could hopefully improve Portland’s “unpredictable commute times.A 2014 Oregonian article mentions that they would also give drivers “a chance to choose an alternate route.”

Street classifications map from ODOT transportation GIS. Annotated by BikePortland.

The “choosing an alternate route” part is becoming a bigger issue now with congestion pricing schemes under discussion and with neighborhoods worried that toll avoidance will lead to more cut through traffic on local streets.

Portland Bureau of Transportation’s (PBOT) response to area traffic has a push-me-pull-me aspect to it. Over the past few years, the bureau has installed traffic calming along several cut-through routes. At the same time, however, it has also maintained the speed limit on those residential streets at 25 mph, even though the streets lack bike facilities or sidewalks in many places.

Hikers scurry across SW Marquam Hill Rd at their trail crossing. The street is posted 25 mph despite lacking sidewalks and its classification as a “local” street. (Photo: Lisa Caballero/BikePortland)

Even on select local streets, PBOT has taken exception to its “20 is Plenty” speed reduction program and maintained a 25 mph posted speed. Where do you find those hand-picked exemptions? On the route from the Sylvan exit to OHSU: Marquam Hill Rd and Gibbs St.

Fairmount to Gibbs is the only route for people riding a bike or walking to campus from the neighborhoods to the west. Yet, as BikePortland recently reported, PBOT’s Development Review department ruled against a new development building sidewalks on its SW Gibbs Street frontage.

Maybe there is something like this going on in your neighborhood too. It is sure to become a more important concern as congestion pricing rolls out. But we aren’t starting from neutral. The purpose, in part, of these reader boards appears to be to encourage cut-through routing. And PBOT seems to be accommodating it with higher speed limits in some places.

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