Why aren’t lane changes allowed on old Narrows Bridge?
June 15th, 2009 by travis baker
The in basket: Richard Hood of Belfair e-mails to say, “All my life, I’ve always wondered why you couldn’t change lanes on the (now old) Tacoma Narrows Bridge. I’ve been told that air passing through the grates could flip your car over, but is that true? I’d really love to know the truth.”
The out basket: That sounds like the product of an overly fertile imagination. I told Richard that I believed that lane changes are recognized among highway designers and enforcement agencies as a major cause of accidents, and in the close quarters of the old bridge, even minor accidents meant major traffic delays for want of somewhere to move the cars.
But Jamie Swift of the Olympic Region of state highways says there’s a more direct reason.
“Lane changes are prohibited on the 1950 bridge,” he said, “due to the difference in friction between the traffic lane and the grates as drivers switch
lanes.” It has nothing to do with air passing up through the grates, which, as I recall, were made part of that bridge to lessen its wind resistance and avoid the calamitous end its predecessor, Galloping Gertie, met.
Original plans for retrofitting the old bridge after the new one opened called for taking out those grates to facilitate making the bridge three wider lanes westbound with a shoulder. But plans changed after public sentiment for four westbound lanes prevailed. As a result, says Claudia Cornish of the bridge staff, “the grates were kept in the bridge deck, and two changes were made to accommodate that design: 1) the right westbound lane now ends at the first exit after the bridge; 2) The fourth lane begins around Sixth Avenue, so when you’re approaching the old bridge, you can get into that fourth lane before you actually reach the bridge.”
I’ll let the engineers and aerodynamics experts in our readership weigh in on whether there’s any chance that air passing through the grates might affect the performance of a car, but I doubt it.
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Tags: bridge, grates, lane changes, no passing, Tacoma Narrows
Scripps Interactive Newspapers Group
June 15th, 2009 at 4:41 pm
Before the signage enforcement, I recall my 1971 VW Beetle would meerly slide across those grates on a wet, rainy night. “Hold on”, I would exclaim! Dangerous indeed. It is not even safe to change lanes on a dry day. My suggestion, don’t make a habit of it, lest you invite trouble for yourself.
June 16th, 2009 at 4:44 pm
“And a subtle change is coming this summer in the optional $5 tab fee add-on to support state parks. That’s the subject of the next Road Warrior.”
Tease.