the shanghai–kowloon through train is an intercity railway service between hung hom station in hong kong and the shanghai railway station, jointly operated by the mtr of hong kong and china's national rail service (shanghai railway bureau). the numbers of this train service is z99b (being away from shanghai) and z100b (being towards shanghai). services operate along the east rail line in hong kong, crossing the boundary between hong kong and mainland china at lo wu/luohu and then continuing along china's railway network via the guangshen railway, jingguang railway and the hukun railway to shanghai. the through train runs every other day. the journey time is approximately 20 hours.