NS has two active track geometry train sets.
The one you mention consists of NS Research platform 38 "The Brick", which was rebuilt using the frame and trucks of former NS/NW EMD SD40 1620. It contains sensing and measuring equipment for track geometry and rail profile (rail wear), as well as the the power supply for itself and NS Research car 36, and is weighted to deflect the track. The Research 36 car contains the recording and processing equipment for the data supplied by NS 38.
The second set includes NS Research 34 platform, which was built on the frame and trucks of what was originally N&W SD35 1530. It is mated with NS Research car 33. This pair works in the same manner as described with NS 38/36.
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