Video: Rail Guideway over H-1

A 30-second video I put together on a whim and shared on Facebook last night has been viewed over 8,000 times, and shared by over 140 people. While not exactly viral content, it did affirm that I wasn’t the only person who is fascinated by big construction projects.

Two major transportation projects are unfolding on my daily drive between Mililani and downtown. The first, widening of the Interstate H-1 freeway westbound between Pearl City and the Waiawa Interchange with H-2 just past the Waipahu exit. The second, the construction of a flyover for the Honolulu rail transit guideway at that same interchange. While the former will clearly have a more tangible impact on the flow of traffic, the latter is much more interesting from an engineering standpoint.

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Construction of the elevated rail guideway began in 2012, but the first pillars and segments were going up over wide-open agricultural land near Kapolei. Construction later reached Fort Weaver Road in Ewa, and is now having an impact along Kamehameha Highway from Waipahu to Pearl City, but it’s still fair to say the guideway span being built right over the freeway near Leeward Community College is the most visible component of the rail project yet.

It was one thing for the city to tell us in April that construction at the interchange going to proceed (starting with a “giant pier column” and then building the the guideway out from there). It was another thing entirely to watch it happen, in slow motion, over the next year.

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I had assumed that crews would build the middle pillar and pillars on either side of the freeway, then lower long pre-cast concrete bridge spans across the top. So it took several weeks of watching that middle pillar get unexpectedly top heavy, and then start to grow out on either side, before I figured out that the ends of the flyover were going to “grow” all the way across the freeway.

It seemed to nearly defy physics. Driving under it day after day, and week under week, I both marveled at the task and harbored fears that the long concrete branch might just snap.

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Of course, it’s not a good thing for drivers to be distracted by irrational fears while commuting, and the city started repeating the mantra, “Look ahead, not overhead.” (And I should note that my photos and videos were captured while I was a passenger, or by strapping my iPhone to my car’s visor and leaving it running the whole way home.) And as the segment over the westbound lanes of H-1 started to come together from opposite sides, the natural question was when — or whether — they would connect.

Hawaii News Now even devoted a segment to the question, describing the work at the Waiawa Interchange as “the most dramatic and intensive portion of the first ten miles” of rail construction. And they also talked about the method of construction, called the “balanced cantilever.”

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I was intrigued by this local implementation of this large-scale engineering strategy. Looking at the H-1 flyover, the distance from the middle pier to the Leeward Community College side of the freeway seemed impossibly wide. But balanced cantilever construction can easily span much, much wider distances.

And it turns out that it’s nothing new for Hawaii… just new to me, driving under it every day. After I posted my video, I heard from a couple of people actually working on the rail project. One of them noted, “That balanced cantilever is time-tested method that was used to construct H-3 and H-2’s Kipapa Gulch crossing.”

I also drive over Kipapa Gulch every day. And H-3? Just look at those massive spans. It makes my inner engineer’s heart go pitter-pat.

When HNN reported the two ends of the guideway were officially connected yesterday, I was inspired to share my video. And the reaction to it (fueled in part by the I Mua Rail group) shows that lots of people are similarly impressed. The video certainly attracted some comments from critics of the rail project, but even some of them offered begrudging admiration.

For rail fans, the good news is, my blurry, washed out photos and videos through my dirty car window aren’t the only record of all this work. I’m told there are time-lapse cameras capturing a lot of the project, in addition to comprehensive video and photo documentation of before, during, and after construction. I can’t wait to see it.

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Bonus: If you want to experience the drive on H-1 westbound from before Pearl City to the H-2 interchange, I’ve also posted longer videos from April and May of this year. These definitely show the changes coming from the freeway widening project.

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3 Responses

  1. Duck Tape says:

    Thank you for the video.

    And no “duck tape” was used to build the cantilever flyover

  1. August 10, 2015

    […] wrote in June about my fascination with the balanced cantilever construction method that connected a long segment of concrete directly over a busy freeway. As a daily commuter from Mililani to Iwilei and back, I saw the work […]

  2. October 19, 2015

    […] know that it’s a little strange to be so obsessed with counting lanes, or in tracking balanced cantilever bridge construction or the continuous-weld sliding truss that’s quickly extending the elevated guideway for our […]

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