There were nineteen Economy Class sittings cars introduced to service 1981/1982. They were classed BN. The numbers were: 1, 2, 4, 5, 7, 8, 10, 11, 13, 14, 16, 17, 19, 20, 22, 23, 25, 26 and 28.
'N' cars were given numbers 1 to 57 and different classes allocated within the number group.
The cars were originally introduced as three car sets; eg 1BN-2BN-3ACN_ ( Set N1 ). However with the introduction of BRN_, Refreshment cars, the original sets were split.
Car sets were numbered N1, N2, etc and were called 'N' sets. By the early 1990's, passenger traffic increased saw the sets increased to four cars. These four car sets were called 'FN' sets.