We're looking at the rear of a track undercutter at work. It digs under the track and puts down a blanket of rubber to protect the track. John caught them at work om an overcast dayt doing Church St. when he was still a teenager.
Thumbnail shows only portion of total image.
We're working out way from the rear toward the front of the unit in this series of photos. You can clearly see the roll of material in this shot. You can see the track lifted up. The machine was clogged when John snapped these pics. The guys are working to undo the problem.