Well, I was right in associating the image of a zipper. They *do* call the Zamboni-thingy a "zipper machine". Here's a URL to see said thingy in action:
http://www.roadstothefuture.com/Zipper_I95_JRB.html
It seems to want to call the medians themselves "temporary" or "moveable" barriers. Edit in: Ye gods, there's an acronym (of course) - the Quickchange Moveable Barrier.

I was half guessing that the search criteria "zipper barrier" might be a decent Google-whack. No such luck. 9,880 hits. If I look hard enough, some of them might reference unfortunate accidents involving the male anatomy...