(Video Link)

Zipper Trucks are amazing machines that quickly pick up and move 1,500 pound blocks of concrete that serve as median barriers on San Francisco's highways:

Each 30-ton, 58-foot Zipper Truck is driven by a two-person team. As it passes over the barrier system, a series of wheels gently lifts each block off the street, funnels it through an S-shaped curve under the vehicle, and deposits the block into the other lane. The entire bridge-rearranging process should take less than ten minutes. When it is completed in the fall of 2013, the $26.5 million project will integrate with the zipper system already installed along the new Doyle Drive, to create a seamless, safe approach to the Golden Gate.

Watch the above video showing a Zipper Truck cruising down Doyle Drive in dense traffic.

Link -via The Presurfer