Train laying it's own track

They are replacing the sleepers and ballast (Belgium, across the border from the Netherlands, near Eindhoven). The machine you see at 4:04 is amazingly strong and laser guided. It picks up the rails, then vibrates the stones underneath the track, so that they fall into each others gaps. The stones have sharp corners and if they are that tightly packed, the bed of stones is stronger than concrete, but can be adjusted at any time. Then the machine places the rails in the stonebed with an accuracy of less than a millimeter. In the Dutch and Belgian railway system, there are no gaps in the rails. The rails are welded together to beams of tens of kilometers long. With this machinery, they can attain the precision required.