FHA wagons are built to allow the carriage of intermodal (road/rail) vehicles within the UK loading gauge. Although relatively rare compared to the liner train concept the wagons allow some traffic to move by rail which would otherwise remain on the road. These wagons were ordered following the successful operation of two prototypes carrying Royal Mail road trailers. Unfortunately the loss of Royal Mail traffic has resulted in them lying idle almost since they were built, this still being the case today.