British Rail Class 99
The British Rail Class 99 was a fleet of 14 ferries, mostly owned by Sealink, which carried rail vehicles between Britain and mainland Europe. When British Rail implemented the TOPS system for managing their operating stock, these ships were incorporated into the system in order to circumvent some of the restrictions of the application software. This allowed them to be counted as locomotives while carrying railway vehicles in the same way as a normal locomotive would haul a train.