Specialised types included AA8 which had a low, central body to allow forward visibility (for the banking locomotive) on the steeply-graded Pontnewynydd line in south Wales; it had an open veranda at each end. AA7 were small 12 ton vans for working over the Metropolitan Railway’s underground lines to Smithfield Market. AA4 were fully enclosed vans for working through the lengthy Severn Tunnel. Other fully enclosed vans were built for use on permanent way trains and were given diagram AA6. The next batch of permanent way vans were rated at 25 tons and fitted with ploughs to spread newly laid ballast (AA10). Diagram AA23 was the last GWR design of TOAD, and several vans from this lot of 326 never saw GWR service, having been completed under British Railways.
