About 1892/1893 twelve _AA_ class bogie carriages were modified with toilets and side corridors. Some dates suggest this occurred as late as 1899.
The twelve AA cars were given a class grouping of their own in about 1902. The group was called AC and the numbers were 1 - 12. These cars were ex AA 17, 28, 33, 45, 53, 57, 72, 75, 77, 94, 106 and 108 respectively.
AC 10 was destroyed in an accident at Kirkstall during January 1906. The vehicle was not "written off" until 1908.
Car AC 12 was recoded to ABC 59, to ABL_ 59 c1910 finally becoming _BL_ 11 in 1918.
The remaining cars were recoded to AL in 1910 with the same numbers retained.
During 1913/1914 all the AL cars were made Second Class carriages and recoded to _BL_ with the same numbers.