Light Show

Traffic signals keep rhythm with the city’s new MAX lines

By Kasey Cordell July 20, 2009 Published in the August 2009 issue of Portland Monthly

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CRUISING THROUGH DOWNTOWN IS A LOT LIKE PLAYING FROGGER: time it just right, and you can zip through all the lights without tapping your brakes. “Right” in this case is 11.8 miles per hour at peak hours (2:06 p.m. to 6:01 p.m.), when traffic signals change on 60-second cycles.

Richard Johnson, the Portland Bureau of Transportation manager who oversees traffic-signal operation, compares the lights’ sequential switch to a kindergarten class singing “Frère Jacques.” “One group starts,” he says, “then a few seconds later another, and another.”

But when new Yellow and Green MAX light-rail trains begin gliding down SW Fifth and Sixth Avenues on September 12, hitting a string of green lights by bike or car won’t be so simple. Johnson explains that MAX trains disrupt the signal cycle, allowing trains to clear by lengthening green lights running north to south while shortening green lights for cross traffic. At junctures like SW Oak Street and W Burnside Street, where MAX trains will pass by up to 10 times an hour, car-clogging bottlenecks could result.

Fortunately, that won’t happen: the city has spent $38,000 for an upgrade to each signal’s internal computer, a change akin to trading in the Commodore 64 (which you might have played Frogger on) to something on par with 1980s-era Macs. Not a huge leap, but big enough to let the system use an algorithm to resynchronize the lights in just one cycle. They’ll even detect when a MAX train leaves a station so that the signals in its path can be red-lighted to clear the way.

A neat trick for light-rail riders, but for motorists waiting at a light, the change could spell “game over” for a perfectly seamless, 11.8 mph, red-light-free cruise through downtown.

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