Rants and Ramblings: random commentary about culture, media, politics, technology and whatnot.

lane shifter

I’ve always wondered about how the transportation powers that be shift the concrete barriers dividing lanes on the Roosevelt Bridge between D.C. and Rosslyn. Today, I came across a video from the Post’s John Kelly where he visits the crew that handles that job with the help of a special “Barrier Transfer Machine.” It’s rather mesmerizing to watch the line of barriers twist and shift into place. The video accompanies a column Kelly wrote about the bridge machine this weekend.

But first, the Quickchange Moveable Barrier, made by a California company called Barrier Systems Inc. Traffic is separated on the bridge by an articulated concrete wall. It’s like a 3,800-foot-long, unfastened bracelet, each link a 600-pound block of reinforced concrete about 3 feet tall, 3 feet wide and a foot deep. The blocks are joined by metal pins and shock absorbers.

As it approached, Jim said, “It’s eating the barriers on one side, and they come out the other side.”

Indeed it was: eating the barriers with a “mouth” on the right side, lifting them up and excreting them 10 feet to the left.

The top of each concrete block has a profile sort of like a champagne cork. It’s that indentation that the barrier transfer machine grabs onto. A pair of rails welded to the underside of the diesel-powered machine are lined with rubber wheels about the size of a Frisbee. The concrete blocks ride up on the rails, roll up and under the machine on the wheels, and get deposited one lane width over. It takes about 25 minutes to do the entire bridge.

The BTM is like the pushmi-pullyu from “Dr. Dolittle.” It has a steering wheel on each end and can drive in both directions. About 4 a.m., it goes from east to west, creating an extra inbound lane. About 10:30 a.m., it goes from west to east, creating an extra outbound lane.

(Washington Post: “Answer Man Undeterred By Concrete, Congestion” - 03/18/07)