NIR MPV No. 11 passing through Botanic heading northbound. What is RHTT? RHTT stands for 'Rail Head Treatment Trains' where they send out a maintenance train such as the MPV to work on the railway lines to cleanse off any obstacles that might have fallen onto the tracks by weaponising their special ingredients known as 'waterjetting' and 'sandite'. The waterjetting helps to clean any contamination on the railhead such as leaves, salt water spray etc… this is then followed up by a layer of sandit