Sure you didn't see FRA T-10 (Ex Budd SPV-2000 demonstrator)?
My guess is that you saw CN 1501, an RDC converted into a track inspection vehicle.
Link to a recent (April 2014) photo (not mine) of CN RDC 1501 in Illinois (this website has several others from that time frame, too - see the 'strip' at the bottom of this page):
http://www.railpictures.net/viewphoto.php?id=477282&nseq=2
- Paul North.
A GREAT LOOKING CAR
Our community is FREE to join. To participate you must either login or register for an account.