This video from looks at the Works Test Train in BR Blue and Grey by Bachmann. The Works Test Train is a pair of Mk1 SK coaches feature extra detailing, heavy weathering and departmental running numbers with an ADB prefix. The Works Test Train was used for test runs after a locomotive completed static testing on a load bank. The locomotive would have to pass tests with the Works Test Train prior to re-entering service following maintenance, overhaul or repairs.