These units were originally built as two-car Class 155 units by British Leyland from 1987 - 1988, but were converted into separate units by Hunslet-Barclay from 1991 - 1992. The layout of the original non-cab ends were different from the original cab end, so the ends are noticeably distinct, and the vehicles are not symmetrical.
Their maximum speed is 75 mph (121 km/h) and are often found working on local services such as the Marston Vale Line from Bedford to Bletchley and the Heart of Wales Line. They are fitted with standard BSI auto-couplers and are therefore able to work in tandem with other multiple units fitted with the same coupler, including Class 142, Class 143, Class 144, Class 150, Class 156 and Class 158 units as well as newer units like the Class 170 DMU.
The new or small cab is significantly smaller than the original Leyland cab and encroaches on the door vestibule area, providing cramped conditions for Drivers and Guards. Similar to other Sprinter units, such as the Classes 150/2, 156 and 158, these units have gangway door connections at either end that allow passengers and staff to walk between units working in multiple. These units also have the benefit of having passenger door control panels at either end of the cars.
For Train Simulator, the Class 153 was developed by Just Trains and published through their website.