On Sun, 17 Oct 2010 20:20:37 -0400, "Jeff Stanton"
FP - Flat Rack car. Ordinary flat car provided with side and end
racks, with door openings in sides. Suitable for handling pulpwood.
XA - Automobile car. Similar in design to "XM", but with
exceptionally large side or side and end doors.
THI - Insulated tank car equipped with heater device which permits
intransit heating of lading. Apparatus operated by power other than
through the axle.
I don't see "TRI" listed; I suspect it is an insulated version of a TR