2: AAR plate C clearances for interchange, from the Official
Railway Equipment Register.
The time-honored NMRA gauge, in HO, measures 21' 6” high
from the railhead and 14' 6” wide, tapering to 8' wide at the
top. It looks a lot like the Association of American Railroads
(AAR) Plate C standard, adopted in 1968 and revised several
times since. Plate C allows 15' 6” of height and 10' 8” of width.
So, what's the big deal? After all, the NMRA gauge allows 6'
more height, and 3' 10” more width.
Trouble is, modern freight cars are long, and they don't always
taper at the top. In 1991, the AAR published Plate F standards,
allowing a maximum car height of 20' 2” above the top of the
2
AAR rail clearances - 2
MRH-Jun 2013
