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Portland Bureau of Transportation

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Secrets of a transportation professional: hitting a green light every time

5 Comments

Among the many benefits of working in the transportation world is learning all of the guild-protected secrets of the profession.  Perhaps you'll remember our past post on how to hit all of the walk signals while ambling downtown?

image courtesy: Curtis Gregory Perry

But our most cherished and protected trade secret is how to get a green light while traveling on city streets. 

Please disregard the urban myth that you can flash your high beams at a red traffic signal to activate some secret, emergency light-changer-thingamajiggy; pure baloney (yes! I used the word baloney).  You can't use your tv's remote either, but I don't believe that any of our readers would buy that anyways.

So what's the secret? Well it depends...(What a bureaucratic answer).  Essentially, if you travel a few mphs below the speed limit many of Portland's streets, particularly our one-way streets, have signals synchronized to turn green in succession.

So, when you're in downtown Portland most of the signals are timed at 12 mph.  Go about 11 and you're golden.  Later in the evening some of the signals increase to about 15 mph - crusing!

On Martin Luther King Jr. Blvd and Grand Ave, travel 27 mph (just slightly below the speed limit of 30 mph) and you'll be basking in the glorious green wave of unimpeded travel. 

Have you noticed this on any other streets?  I promise you this - there are a lot more!  Portland has updated hundreds of signals to reduce congestion and air pollution and increase automobile efficiency.

5 Comments

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1

Michael Andersen

December 5, 2010 at 11:06 PM

Okay, Scott, question: If I'm traveling at, say, exactly 1/2 or 1/3 of the optimum speed, will I see the same efficiencies?

If not, is there a way to calculate optimum bike or walking speeds given an optimum car speed -- involving, perhaps, the duration of the red light?

2

Michelle Lasley

December 6, 2010 at 5:21 AM

How do side streets that trigger stop lights factor into the equation? My husband gets frustrated with the "ghost car" that makes the light change, but is really not there.

In North Portland, we can verify that Lombard does not follow this theory whether you're traveling at 30, 33, or 35 (posted limit is 35).

The street that works best for me? (Dare I say this lest I jinx myself and its timed effeciency?) Broadway, east, slightly over at 32.

And, boy do I miss Naito's timing. After the "improvements" to the street, the lovely timing that made life efficient disappeared.

So, my real question is: what happened to the grant that Adams tried to secure as commissioner that was supposed to study the emissions and work towards better light timing?

3

Scott Cohen

December 6, 2010 at 8:49 AM

Michelle - Indeed Lombard's lights most likely are not synchronized the way MLK/Grand or Broadway/Weidler are, for example. Synchronization works best on one-way streets and couplets.

As for the grant, I'm not 100% sure which one you are referring to, but we did secure some funding for signalization work (http://climatechange.transportation.org/statelocal_mpo/local_metropolitan_areas.aspx#21).

Side streets won't affect signal that are synchronized - however, at certain times (like late at night) the signals may switch to triggering, rather than timing.

4

Scott Cohen

December 6, 2010 at 8:49 AM

Michael - Most of the signals that I know are synchronized are timed for automobile traffic, and I'm not smart enough to do the logarithm that will calculate a slower speed that would also provide the "green wave" for waling or biking. However, PBOT has changed some signal timing to enhance bicycle travel (Williams and NE Broadway traveling northbound, for example).

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Spam Prevention In the Pacific Northwest, what state is Portland in?