Track geometry car! Number 33

What you saw was the NS track geometry train for measuring and recording track profile.
The track geometry slug, NS 34, originally started off its life as Norfolk and Western SD35 No. 1530, delivered in 8/65.   It was demolished in a wreck at Lynchburg, VA in in 5/76 when it hit a standing ballast train at track speed.  It was rebuilt by the N&W Roanoke Shops and outshopped as N&W RP-E6 (Remote Power - EMD 6-axle) road slug No. 9921. This unit and sister 9920 (rebuilt from a wrecked Erie Lackawanna SDP45) were each mated between a pair of SD45 masters.   The 9921 was renumbered to N&W 9951 in 5/81. 
Following the N&W and Southern Railway merger in 1982, the slug became NS 9951.  It was retired and placed into storage in 10/89 and then leased to the Wheeling & Lake Erie Railway in 5/90.  It was returned from the W&LE in 9/92 and once again retired and placed into storage. 
In 7/94, the NS Roanoke Shops began work on the 9951 to convert it for track geometry operations.  Work on the unit took place over a period of five years when things were slow in the shops and it was finally released as NS 34 in 7/99.  The slug carbody had been rebuilt with taller areas at each end, the fuel tank had been shortened, the traction motors had been removed with track measuring devices added to one truck, and a generator had been installed in the carbody to power the measuring equipment.  The unit was painted in NS tuscan red and lettered in dulux gold.
I can't find my data on NS Research car No. 33, but if I recall correctly this car was purchased from Union Pacific specifically for conversion to track geometry duty.