NIR MPV No. 11 passes Seahill with the EX 12:50 Portadown run bound for Bangor. What is RHTT? RHTT stands for Rail Head Treatment Trains. On an annual basis, mainly around the autumn/winter season, they send out special maintenance trains such as the MPV to maintain the railway in good working condition. The MPV contains special properties to dealing with any leaf fall that may potentially have landed on the rail head. These are known as 'waterjetting' and 'sandite'. The waterjetting helps to cl