When I drive on the Roosevelt Bridge from VA to DC I often see something that looks like a kind of a streetcar-looking thing straddling the jersey wall. The wall is different than most in that it has short sections, maybe 3’ long, with large gaps, maybe 3-4", between each section. It is specifically designed to straddle this wall. I suppose it serves some sort of maintenance purpose; it does not carry passengers and moves too slowly to be useful for transportation. Once I have seen it being driven, but its function was not obvious.
Are you talking about the machine which moves the central barrier to make the lane go one or the or the other way? It moves the barrier from one side of the lane to the other side.
Pretty slick. I saw it operating this morning and now that I know what it is, I could see what it was doing. Normally when you pass it while driving at 50 MPH you can’t get a good look, but I glanced over and it was snaking the barrier over and moving pretty quickly for what it was doing.