Thousand shoulders

How do you build a highway flyover without closing the road directly below it? In Indonesia, you build the pylons sideways and then rotate them into position.

Gunawan Kartapranata / CC BY-SA

1980s Jakarta had a serious road congestion problem. The solution was to build toll highways above existing roads… but that would involve closing the roads while the highway flyovers were being built, and that would create even worse congestion.

The Indonesian engineer Tjokorda Raka Sukawati came up with a novel solution. Build the pylons in the median strip (or close one lane in the middle of the road), but mount the top of each pylon sideways. Once it’s in place, rotate the top of the pylon into place and put the road on top of it. The elevated highway is complete, and the road below it never stops.

I’m guessing that this is a little difficult to visualize. You can watch the video at the end of this post – if you don’t mind corporate boasting and canned music – or read on. It may help to think of the major components of an elevated highway / flyover:

  1. The huge concrete pylons that hold the whole thing up
  2. The tops of the pylons, long beams stretching out like the top of an uppercase T
  3. The road surface, set on top of those beams

Sukawati’s solution was to put the beams on sideways, parallel with the road below. While being built they would never overhang the road, so you could leave it open and operational the whole time. Once everything was ready, a bunch of oil is pumped between the pylon and the beam, and then the whole beam is gently nudged 90 degrees around and into place. Instant highway! (Well, it takes 30 minutes to move that 480 tonne beam into place, but that’s still pretty fast.)

This technique is known as sosrobahu, from the Old Javanese word for a thousand shoulders. It is still used in Indonesia, and has also been employed in the Philippines, Malaysia, and Japan.


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