For the operation of two car sets, driving trailer cars were used in 'Motor -Driving Trailer Car' configuration. For sliding door stock, the class was designated BCPD.
The car numbers for this group were: 2, 3, 8, 9 and 18. These cars were converted from BCP_ cars, same numbers retained; BCP 2 to BCPD 2, etc. These cars were converted between February and June of 1921.
As of late 1921 the electric stock codes were changed. Early in 1922 the BCPD cars were relettered to _D__. Cars 2, 3, 8, 9 and 18 became D 211, 204, 205, 206 and 207 respectively.
At this time more trailer car conversions were progressing but these vehicles were lettered straight into the D group.